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Systems in Two Variables
                           Graphing
                        Substitution
             Elimination by Addition
                        Applications




       Math 1300 Finite Mathematics
Section 4.1 Review: Systems of Linear Equations in Two
                      Variables


                          Jason Aubrey

                     Department of Mathematics
                       University of Missouri




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                      Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                                Graphing
                             Substitution
                  Elimination by Addition
                             Applications




Definition (Systems of Equations in Two Variables)
Given the linear system

                                 ax + by = h
                                 cx + dy = k

A pair of numbers x = x0 , y = y0 [also written as an ordered
pair (x0 , y0 ) is said to be a solution of the system if each
equation is satisfied by the pair. The set of all such ordered
pairs is called the solution set for the system. To solve a
system is to find its solution set.


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                           Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                                Graphing
                             Substitution
                  Elimination by Addition
                             Applications




Definition (Systems of Equations in Two Variables)
Given the linear system

                                 ax + by = h
                                 cx + dy = k

A pair of numbers x = x0 , y = y0 [also written as an ordered
pair (x0 , y0 ) is said to be a solution of the system if each
equation is satisfied by the pair. The set of all such ordered
pairs is called the solution set for the system. To solve a
system is to find its solution set.

We will consider three methods for solving such systems:
graphing, substitution, and elimination by addition.                       university-logo



                           Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                                 Graphing
                              Substitution
                   Elimination by Addition
                              Applications


Example: Solve the linear system by graphing:

                                    3x − y = 2
                                    x + 2y = 10



       10
        8
        6
        4
        2

  −4 −2      2     4     6      8    10                                     university-logo
      −2

                             Jason Aubrey    Math 1300 Finite Mathematics
Systems in Two Variables
                                 Graphing
                              Substitution
                   Elimination by Addition
                              Applications


Example: Solve the linear system by graphing:

                                    3x − y = 2
                                    x + 2y = 10



       10
        8
        6
        4
        2

  −4 −2      2     4     6      8    10                                     university-logo
      −2

                             Jason Aubrey    Math 1300 Finite Mathematics
Systems in Two Variables
                                 Graphing
                              Substitution
                   Elimination by Addition
                              Applications


Example: Solve the linear system by graphing:

                                    3x − y = 2
                                    x + 2y = 10



       10
        8
        6
        4
        2

  −4 −2      2     4     6      8    10                                     university-logo
      −2

                             Jason Aubrey    Math 1300 Finite Mathematics
Systems in Two Variables
                                 Graphing
                              Substitution
                   Elimination by Addition
                              Applications


Example: Solve the linear system by graphing:

                                     3x − y = 2
                                     x + 2y = 10



       10
        8
        6
                 (2, 4)
        4
        2

  −4 −2      2     4      6      8    10                                    university-logo
      −2

                              Jason Aubrey   Math 1300 Finite Mathematics
Systems in Two Variables
                                Graphing
                             Substitution
                  Elimination by Addition
                             Applications




Definition (Systems of Linear Equations: Basic Terms)
A system of linear equations is consistent if it has one or more
solutions and inconsistent if no solutions exist. Furthermore, a
consistent system is said to be independent if it has exactly
one solution and dependent if it has more than one solution.
Two systems of equations are equivalent if they have the same
solution set.




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                           Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                               Graphing
                            Substitution
                 Elimination by Addition
                            Applications




Theorem (Possible Solutions to a Linear System)
The linear system

                                ax + by = h
                                cx + dy = k




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                          Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                               Graphing
                            Substitution
                 Elimination by Addition
                            Applications




Theorem (Possible Solutions to a Linear System)
The linear system

                                ax + by = h
                                cx + dy = k

Must have
    Exactly one solution (consistent and independent), or




                                                                          university-logo



                          Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                               Graphing
                            Substitution
                 Elimination by Addition
                            Applications




Theorem (Possible Solutions to a Linear System)
The linear system

                                ax + by = h
                                cx + dy = k

Must have
    Exactly one solution (consistent and independent), or
    No solution (inconsistent), or



                                                                          university-logo



                          Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                               Graphing
                            Substitution
                 Elimination by Addition
                            Applications




Theorem (Possible Solutions to a Linear System)
The linear system

                                ax + by = h
                                cx + dy = k

Must have
    Exactly one solution (consistent and independent), or
    No solution (inconsistent), or
    Infinitely many solutions (consistent and dependent).


                                                                          university-logo



                          Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                                Graphing
                             Substitution
                  Elimination by Addition
                             Applications




Theorem (Possible Solutions to a Linear System)
The linear system

                                 ax + by = h
                                 cx + dy = k

Must have
    Exactly one solution (consistent and independent), or
    No solution (inconsistent), or
    Infinitely many solutions (consistent and dependent).
There are no other possibilities.
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                           Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                                Graphing
                             Substitution
                  Elimination by Addition
                             Applications




Example: Graph the equations and find the coordinates of any
points where two or more lines intersect. Discuss the nature of
the solution set.

                                x − 2y = −6
                                2x + y = 8
                                x + 2y = −2




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                           Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                                   Graphing
                                Substitution
                     Elimination by Addition
                                Applications




           6


           4


           2



−4   −2        0        2          4

          −2


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                              Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                                   Graphing
                                Substitution
                     Elimination by Addition
                                Applications




           6
                                                                  x − 2y = −6
           4


           2



−4   −2        0        2          4

          −2


                                                                                university-logo



                              Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                                   Graphing
                                Substitution
                     Elimination by Addition
                                Applications




           6
                                                                  x − 2y = −6
           4                                                      2x + y = 8

           2



−4   −2        0        2          4

          −2


                                                                                university-logo



                              Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                                   Graphing
                                Substitution
                     Elimination by Addition
                                Applications




           6
                                                                  x − 2y = −6
           4                                                      2x + y = 8
                                                                  x + 2y = −2
           2



−4   −2        0        2          4

          −2


                                                                                university-logo



                              Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                                   Graphing
                                Substitution
                     Elimination by Addition
                                Applications




           6
                        (2, 4)                                    x − 2y = −6
           4                                                      2x + y = 8
                                                                  x + 2y = −2
           2



−4   −2        0        2          4

          −2


                                                                                university-logo



                              Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                                   Graphing
                                Substitution
                     Elimination by Addition
                                Applications




           6
                        (2, 4)                                    x − 2y = −6
           4                                                      2x + y = 8
     (−2, 2)
                                                                  x + 2y = −2
           2



−4   −2        0        2          4

          −2


                                                                                university-logo



                              Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                                   Graphing
                                Substitution
                     Elimination by Addition
                                Applications




           6
                        (2, 4)                                    x − 2y = −6
           4                                                      2x + y = 8
     (−2, 2)
                                                                  x + 2y = −2
           2
                                                         No point lies on all
                                                         three lines. So, no so-
−4   −2        0        2          4     ( 14 , − 4 )
                                            3     3      lution to this system.
          −2


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                              Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                               Graphing
                            Substitution
                 Elimination by Addition
                            Applications



Example: Solve the linear system by substitution:

                               2x + y = 6
                                  x − y = −3




                                                                          university-logo



                          Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                               Graphing
                            Substitution
                 Elimination by Addition
                            Applications



Example: Solve the linear system by substitution:

                               2x + y = 6
                                  x − y = −3


                  2x + y = 6




                                                                          university-logo



                          Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                               Graphing
                            Substitution
                 Elimination by Addition
                            Applications



Example: Solve the linear system by substitution:

                               2x + y = 6
                                  x − y = −3


                  2x + y = 6
                           y = 6 − 2x          now substitute:




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                          Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                               Graphing
                            Substitution
                 Elimination by Addition
                            Applications



Example: Solve the linear system by substitution:

                               2x + y = 6
                                  x − y = −3


                  2x + y = 6
                           y = 6 − 2x          now substitute:
                    x − y = −3




                                                                          university-logo



                          Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                               Graphing
                            Substitution
                 Elimination by Addition
                            Applications



Example: Solve the linear system by substitution:

                               2x + y = 6
                                  x − y = −3


                  2x + y = 6
                           y = 6 − 2x          now substitute:
                    x − y = −3
           x − (6 − 2x) = −3




                                                                          university-logo



                          Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                               Graphing
                            Substitution
                 Elimination by Addition
                            Applications



Example: Solve the linear system by substitution:

                               2x + y = 6
                                  x − y = −3


                  2x + y = 6
                           y = 6 − 2x          now substitute:
                    x − y = −3
           x − (6 − 2x) = −3
                  3x − 6 = −3


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                          Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                               Graphing
                            Substitution
                 Elimination by Addition
                            Applications



Example: Solve the linear system by substitution:

                               2x + y = 6
                                  x − y = −3


                  2x + y = 6
                           y = 6 − 2x          now substitute:
                    x − y = −3
           x − (6 − 2x) = −3
                  3x − 6 = −3
                           x =1

                                                                          university-logo



                          Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                                  Graphing
                               Substitution
                    Elimination by Addition
                               Applications



Example: Solve the linear system by substitution:

                                  2x + y = 6
                                     x − y = −3


                     2x + y = 6
                              y = 6 − 2x          now substitute:
                       x − y = −3
             x − (6 − 2x) = −3
                     3x − 6 = −3
                              x =1

Substituting we obtain y = 4. So, the solution is the point (1, 4).
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                             Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                           Graphing
                        Substitution
             Elimination by Addition
                        Applications




Graphing and substitution work well for systems involving
two variables.




                                                                      university-logo



                      Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                           Graphing
                        Substitution
             Elimination by Addition
                        Applications




Graphing and substitution work well for systems involving
two variables.
However, neither is easily extended to larger systems.




                                                                      university-logo



                      Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                           Graphing
                        Substitution
             Elimination by Addition
                        Applications




Graphing and substitution work well for systems involving
two variables.
However, neither is easily extended to larger systems.
Elimination by addition is the most important method of
solution.




                                                                      university-logo



                      Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                           Graphing
                        Substitution
             Elimination by Addition
                        Applications




Graphing and substitution work well for systems involving
two variables.
However, neither is easily extended to larger systems.
Elimination by addition is the most important method of
solution.
It readily generalizes to larger systems and forms the basis
for computer-based solution methods.



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                      Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                                Graphing
                             Substitution
                  Elimination by Addition
                             Applications




Theorem (Operations that Produce Equivalent Systems)
A system of linear equations is transformed into an equivalent
system if




                                                                           university-logo



                           Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                                Graphing
                             Substitution
                  Elimination by Addition
                             Applications




Theorem (Operations that Produce Equivalent Systems)
A system of linear equations is transformed into an equivalent
system if
(A) Two equations are interchanged.




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                           Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                                Graphing
                             Substitution
                  Elimination by Addition
                             Applications




Theorem (Operations that Produce Equivalent Systems)
A system of linear equations is transformed into an equivalent
system if
(A) Two equations are interchanged.
(B) An equation is multiplied by a nonzero constant.




                                                                           university-logo



                           Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                                Graphing
                             Substitution
                  Elimination by Addition
                             Applications




Theorem (Operations that Produce Equivalent Systems)
A system of linear equations is transformed into an equivalent
system if
(A) Two equations are interchanged.
(B) An equation is multiplied by a nonzero constant.
(C) A constant multiple of one equation is added to another
    equation.



                                                                           university-logo



                           Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                               Graphing
                            Substitution
                 Elimination by Addition
                            Applications




Example: Solve the linear system using elimination by addition

                               3u − 2v = 12
                               7u + 2v = 8




                                                                          university-logo



                          Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                               Graphing
                            Substitution
                 Elimination by Addition
                            Applications




Example: Solve the linear system using elimination by addition

                               3u − 2v = 12
                               7u + 2v = 8

                                3u − 2v = 12




                                                                          university-logo



                          Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                               Graphing
                            Substitution
                 Elimination by Addition
                            Applications




Example: Solve the linear system using elimination by addition

                               3u − 2v = 12
                               7u + 2v = 8

                              3u − 2v = 12
                              +7u + 2v = 8




                                                                          university-logo



                          Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                               Graphing
                            Substitution
                 Elimination by Addition
                            Applications




Example: Solve the linear system using elimination by addition

                               3u − 2v = 12
                               7u + 2v = 8

                              3u − 2v = 12
                              +7u + 2v = 8
                               10u + 0 = 20




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                          Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                               Graphing
                            Substitution
                 Elimination by Addition
                            Applications




Example: Solve the linear system using elimination by addition

                               3u − 2v = 12
                               7u + 2v = 8

                              3u − 2v = 12
                              +7u + 2v = 8
                               10u + 0 = 20
                                      u=2



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                          Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                                Graphing
                             Substitution
                  Elimination by Addition
                             Applications




Example: Solve the linear system using elimination by addition

                                3u − 2v = 12
                                7u + 2v = 8

                               3u − 2v = 12
                               +7u + 2v = 8
                                10u + 0 = 20
                                       u=2

Substituting, we obtain v = −3. So the solution is (2,-3)

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                           Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                               Graphing
                            Substitution
                 Elimination by Addition
                            Applications



Example: Solve using elimination by addition.

                              3x − 2y = 8
                              2x + 5y = −1




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                          Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                               Graphing
                            Substitution
                 Elimination by Addition
                            Applications



Example: Solve using elimination by addition.

                              3x − 2y = 8
                              2x + 5y = −1

We multiply the first equation by 5 and the bottom equation by 2
and then add.




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                          Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                               Graphing
                            Substitution
                 Elimination by Addition
                            Applications



Example: Solve using elimination by addition.

                              3x − 2y = 8
                              2x + 5y = −1

We multiply the first equation by 5 and the bottom equation by 2
and then add.
                            15x − 10y = 40




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                          Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                               Graphing
                            Substitution
                 Elimination by Addition
                            Applications



Example: Solve using elimination by addition.

                              3x − 2y = 8
                              2x + 5y = −1

We multiply the first equation by 5 and the bottom equation by 2
and then add.
                            15x − 10y = 40
                             4x + 10y = −2




                                                                          university-logo



                          Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                               Graphing
                            Substitution
                 Elimination by Addition
                            Applications



Example: Solve using elimination by addition.

                              3x − 2y = 8
                              2x + 5y = −1

We multiply the first equation by 5 and the bottom equation by 2
and then add.
                            15x − 10y = 40
                             4x + 10y = −2
                                  19x = 38



                                                                          university-logo



                          Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                                Graphing
                             Substitution
                  Elimination by Addition
                             Applications



Example: Solve using elimination by addition.

                               3x − 2y = 8
                               2x + 5y = −1

We multiply the first equation by 5 and the bottom equation by 2
and then add.
                             15x − 10y = 40
                              4x + 10y = −2
                                   19x = 38
                                                                            1
Now we multiply both sides of this last equation by                        19   to obtain
x = 2.
                                                                                        university-logo



                           Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                                 Graphing
                              Substitution
                   Elimination by Addition
                              Applications



Example: Solve using elimination by addition.

                                3x − 2y = 8
                                2x + 5y = −1

We multiply the first equation by 5 and the bottom equation by 2
and then add.
                              15x − 10y = 40
                               4x + 10y = −2
                                    19x = 38
                                                     1
Now we multiply both sides of this last equation by 19 to obtain
x = 2. Then we substitute back into either of the two original
equations to obtain y = −1.                                    university-logo



                            Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                               Graphing
                            Substitution
                 Elimination by Addition
                            Applications




Example: At $4.80 per bushel, the annual supply for soybeans
in the Midwest is 1.9 billion bushels and the annual demand is
2.0 billion bushels. When the price increases to $5.10 per
bushel, the annual supply increases to 2.1 billion bushels and
the annual demand decreases to 1.8 billion bushels. Assume
that the supply and demand equations are linear.




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                          Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                                Graphing
                             Substitution
                  Elimination by Addition
                             Applications




(a) Find the supply equation.




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                           Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                                Graphing
                             Substitution
                  Elimination by Addition
                             Applications




(a) Find the supply equation.
We wish to find an equation of the form p = mq + b where p
represents unit price and q represents quantity demanded.
We have two points (q, p) on the graph of the supply equation:
(1.9, 4.80) and (2.1, 5.10).




                                                                           university-logo



                           Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                                 Graphing
                              Substitution
                   Elimination by Addition
                              Applications




(a) Find the supply equation.
We wish to find an equation of the form p = mq + b where p
represents unit price and q represents quantity demanded.
We have two points (q, p) on the graph of the supply equation:
(1.9, 4.80) and (2.1, 5.10).
The slope of this line is:




                                                                            university-logo



                            Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                                 Graphing
                              Substitution
                   Elimination by Addition
                              Applications




(a) Find the supply equation.
We wish to find an equation of the form p = mq + b where p
represents unit price and q represents quantity demanded.
We have two points (q, p) on the graph of the supply equation:
(1.9, 4.80) and (2.1, 5.10).
The slope of this line is:

                             5.10 − 4.80   0.3   3
                   m=                    =     =
                              2.1 − 1.9    0.2   2


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                            Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                                Graphing
                             Substitution
                  Elimination by Addition
                             Applications




Therefore the equation of this line is




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                           Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                                Graphing
                             Substitution
                  Elimination by Addition
                             Applications




Therefore the equation of this line is

                                     3
                  p − 4.8 =            (q − 1.9)
                                     2




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                           Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                                Graphing
                             Substitution
                  Elimination by Addition
                             Applications




Therefore the equation of this line is

                                3
                  p − 4.8 =       (q − 1.9)
                                2
                                3     3
                             p = q − (1.9) + 4.8
                                2     2




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                           Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                                Graphing
                             Substitution
                  Elimination by Addition
                             Applications




Therefore the equation of this line is

                                3
                  p − 4.8 =       (q − 1.9)
                                2
                                3     3
                             p = q − (1.9) + 4.8
                                2     2
                                3
                             p = q + 1.95
                                2




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                           Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                               Graphing
                            Substitution
                 Elimination by Addition
                            Applications


(b) Find the demand equation.




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                          Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                               Graphing
                            Substitution
                 Elimination by Addition
                            Applications


(b) Find the demand equation.
Again, we want an equation of the form p = mq + b. We have
two points on the graph of the demand equation: (2.0, 4.80)
and (1.8, 5.10).




                                                                          university-logo



                          Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                               Graphing
                            Substitution
                 Elimination by Addition
                            Applications


(b) Find the demand equation.
Again, we want an equation of the form p = mq + b. We have
two points on the graph of the demand equation: (2.0, 4.80)
and (1.8, 5.10).
The slope of this line is:
                      5.10 − 4.80    0.3    3
                m=                =−     =−
                        1.8 − 2.0    0.2    2




                                                                          university-logo



                          Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                               Graphing
                            Substitution
                 Elimination by Addition
                            Applications


(b) Find the demand equation.
Again, we want an equation of the form p = mq + b. We have
two points on the graph of the demand equation: (2.0, 4.80)
and (1.8, 5.10).
The slope of this line is:
                      5.10 − 4.80      0.3    3
                m=                 =−      =−
                        1.8 − 2.0      0.2    2
Therefore the equation of this line is
                               3
                p − 4.80 = − (q − 2.0)
                               2



                                                                          university-logo



                          Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                               Graphing
                            Substitution
                 Elimination by Addition
                            Applications


(b) Find the demand equation.
Again, we want an equation of the form p = mq + b. We have
two points on the graph of the demand equation: (2.0, 4.80)
and (1.8, 5.10).
The slope of this line is:
                      5.10 − 4.80      0.3    3
                m=                 =−      =−
                        1.8 − 2.0      0.2    2
Therefore the equation of this line is
                               3
                p − 4.80 = − (q − 2.0)
                               2
                               3     3
                        p = − q + (2.0) + 4.80
                               2     2
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                          Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                               Graphing
                            Substitution
                 Elimination by Addition
                            Applications


(b) Find the demand equation.
Again, we want an equation of the form p = mq + b. We have
two points on the graph of the demand equation: (2.0, 4.80)
and (1.8, 5.10).
The slope of this line is:
                      5.10 − 4.80      0.3    3
                m=                 =−      =−
                        1.8 − 2.0      0.2    2
Therefore the equation of this line is
                               3
                p − 4.80 = − (q − 2.0)
                               2
                               3     3
                        p = − q + (2.0) + 4.80
                               2     2
                               3
                        p = − q + 7.80                                    university-logo
                               2
                          Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                                Graphing
                             Substitution
                  Elimination by Addition
                             Applications




(c) Find the equilibrium price and quantity.




                                                                           university-logo



                           Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                                Graphing
                             Substitution
                  Elimination by Addition
                             Applications




(c) Find the equilibrium price and quantity.
We set supply equal to demand and solve:

               3          3
              − q + 7.80 = q + 1.95
               2          2




                                                                           university-logo



                           Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                                Graphing
                             Substitution
                  Elimination by Addition
                             Applications




(c) Find the equilibrium price and quantity.
We set supply equal to demand and solve:

               3           3
              − q + 7.80 = q + 1.95
               2           2
                      3q = 5.85




                                                                           university-logo



                           Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                                Graphing
                             Substitution
                  Elimination by Addition
                             Applications




(c) Find the equilibrium price and quantity.
We set supply equal to demand and solve:

               3           3
              − q + 7.80 = q + 1.95
               2           2
                      3q = 5.85
                                q = 1.95 billion bushels




                                                                           university-logo



                           Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                                Graphing
                             Substitution
                  Elimination by Addition
                             Applications




(c) Find the equilibrium price and quantity.
We set supply equal to demand and solve:

               3           3
              − q + 7.80 = q + 1.95
               2           2
                      3q = 5.85
                                q = 1.95 billion bushels

Substituting, we find p = − 3 (1.95) + 7.80 = $4.88
                           2



                                                                           university-logo



                           Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                               Graphing
                            Substitution
                 Elimination by Addition
                            Applications




(d) Graph the two equations in the same coordinate system and
identify the equilibrium point, supply curve, and demand curve.




                                                                          university-logo



                          Jason Aubrey     Math 1300 Finite Mathematics
Systems in Two Variables
                                      Graphing
                                   Substitution
                        Elimination by Addition
                                   Applications



f
    (d) Graph the two equations in the same coordinate system and
    identify the equilibrium point, supply curve, and demand curve.


    6


    4


    2



        0   2     4          6         8          10         12

                                                                                      university-logo



                                 Jason Aubrey          Math 1300 Finite Mathematics
Systems in Two Variables
                                      Graphing
                                   Substitution
                        Elimination by Addition
                                   Applications



f
    (d) Graph the two equations in the same coordinate system and
    identify the equilibrium point, supply curve, and demand curve.


    6


    4


    2



        0   2     4          6         8          10         12
g
                                                                                      university-logo



                                 Jason Aubrey          Math 1300 Finite Mathematics
Systems in Two Variables
                                       Graphing
                                    Substitution
                         Elimination by Addition
                                    Applications



f
    (d) Graph the two equations in the same coordinate system and
    identify the equilibrium point, supply curve, and demand curve.


    6
                (1.95, 4.88)
    4


    2



        0   2      4          6         8          10         12
g
                                                                                       university-logo



                                  Jason Aubrey          Math 1300 Finite Mathematics
Systems in Two Variables
                                       Graphing
                                    Substitution
                         Elimination by Addition
                                    Applications



f
    (d) Graph the two equations in the same coordinate system and
    identify the equilibrium point, supply curve, and demand curve.

                       Supply Curve
    6
                (1.95, 4.88)
    4


    2



        0   2      4          6         8          10         12
g
                                                                                       university-logo



                                  Jason Aubrey          Math 1300 Finite Mathematics
Systems in Two Variables
                                       Graphing
                                    Substitution
                         Elimination by Addition
                                    Applications



f
    (d) Graph the two equations in the same coordinate system and
    identify the equilibrium point, supply curve, and demand curve.

                       Supply Curve
    6
                (1.95, 4.88)
    4


    2                   Demand Curve


        0   2      4          6         8          10         12
g
                                                                                       university-logo



                                  Jason Aubrey          Math 1300 Finite Mathematics

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Math 1300: Section 4-1 Review: Systems of Linear Equations in Two Variables

  • 1. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Math 1300 Finite Mathematics Section 4.1 Review: Systems of Linear Equations in Two Variables Jason Aubrey Department of Mathematics University of Missouri university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 2. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Definition (Systems of Equations in Two Variables) Given the linear system ax + by = h cx + dy = k A pair of numbers x = x0 , y = y0 [also written as an ordered pair (x0 , y0 ) is said to be a solution of the system if each equation is satisfied by the pair. The set of all such ordered pairs is called the solution set for the system. To solve a system is to find its solution set. university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 3. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Definition (Systems of Equations in Two Variables) Given the linear system ax + by = h cx + dy = k A pair of numbers x = x0 , y = y0 [also written as an ordered pair (x0 , y0 ) is said to be a solution of the system if each equation is satisfied by the pair. The set of all such ordered pairs is called the solution set for the system. To solve a system is to find its solution set. We will consider three methods for solving such systems: graphing, substitution, and elimination by addition. university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 4. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Example: Solve the linear system by graphing: 3x − y = 2 x + 2y = 10 10 8 6 4 2 −4 −2 2 4 6 8 10 university-logo −2 Jason Aubrey Math 1300 Finite Mathematics
  • 5. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Example: Solve the linear system by graphing: 3x − y = 2 x + 2y = 10 10 8 6 4 2 −4 −2 2 4 6 8 10 university-logo −2 Jason Aubrey Math 1300 Finite Mathematics
  • 6. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Example: Solve the linear system by graphing: 3x − y = 2 x + 2y = 10 10 8 6 4 2 −4 −2 2 4 6 8 10 university-logo −2 Jason Aubrey Math 1300 Finite Mathematics
  • 7. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Example: Solve the linear system by graphing: 3x − y = 2 x + 2y = 10 10 8 6 (2, 4) 4 2 −4 −2 2 4 6 8 10 university-logo −2 Jason Aubrey Math 1300 Finite Mathematics
  • 8. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Definition (Systems of Linear Equations: Basic Terms) A system of linear equations is consistent if it has one or more solutions and inconsistent if no solutions exist. Furthermore, a consistent system is said to be independent if it has exactly one solution and dependent if it has more than one solution. Two systems of equations are equivalent if they have the same solution set. university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 9. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Theorem (Possible Solutions to a Linear System) The linear system ax + by = h cx + dy = k university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 10. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Theorem (Possible Solutions to a Linear System) The linear system ax + by = h cx + dy = k Must have Exactly one solution (consistent and independent), or university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 11. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Theorem (Possible Solutions to a Linear System) The linear system ax + by = h cx + dy = k Must have Exactly one solution (consistent and independent), or No solution (inconsistent), or university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 12. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Theorem (Possible Solutions to a Linear System) The linear system ax + by = h cx + dy = k Must have Exactly one solution (consistent and independent), or No solution (inconsistent), or Infinitely many solutions (consistent and dependent). university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 13. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Theorem (Possible Solutions to a Linear System) The linear system ax + by = h cx + dy = k Must have Exactly one solution (consistent and independent), or No solution (inconsistent), or Infinitely many solutions (consistent and dependent). There are no other possibilities. university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 14. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Example: Graph the equations and find the coordinates of any points where two or more lines intersect. Discuss the nature of the solution set. x − 2y = −6 2x + y = 8 x + 2y = −2 university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 15. Systems in Two Variables Graphing Substitution Elimination by Addition Applications 6 4 2 −4 −2 0 2 4 −2 university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 16. Systems in Two Variables Graphing Substitution Elimination by Addition Applications 6 x − 2y = −6 4 2 −4 −2 0 2 4 −2 university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 17. Systems in Two Variables Graphing Substitution Elimination by Addition Applications 6 x − 2y = −6 4 2x + y = 8 2 −4 −2 0 2 4 −2 university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 18. Systems in Two Variables Graphing Substitution Elimination by Addition Applications 6 x − 2y = −6 4 2x + y = 8 x + 2y = −2 2 −4 −2 0 2 4 −2 university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 19. Systems in Two Variables Graphing Substitution Elimination by Addition Applications 6 (2, 4) x − 2y = −6 4 2x + y = 8 x + 2y = −2 2 −4 −2 0 2 4 −2 university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 20. Systems in Two Variables Graphing Substitution Elimination by Addition Applications 6 (2, 4) x − 2y = −6 4 2x + y = 8 (−2, 2) x + 2y = −2 2 −4 −2 0 2 4 −2 university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 21. Systems in Two Variables Graphing Substitution Elimination by Addition Applications 6 (2, 4) x − 2y = −6 4 2x + y = 8 (−2, 2) x + 2y = −2 2 No point lies on all three lines. So, no so- −4 −2 0 2 4 ( 14 , − 4 ) 3 3 lution to this system. −2 university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 22. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Example: Solve the linear system by substitution: 2x + y = 6 x − y = −3 university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 23. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Example: Solve the linear system by substitution: 2x + y = 6 x − y = −3 2x + y = 6 university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 24. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Example: Solve the linear system by substitution: 2x + y = 6 x − y = −3 2x + y = 6 y = 6 − 2x now substitute: university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 25. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Example: Solve the linear system by substitution: 2x + y = 6 x − y = −3 2x + y = 6 y = 6 − 2x now substitute: x − y = −3 university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 26. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Example: Solve the linear system by substitution: 2x + y = 6 x − y = −3 2x + y = 6 y = 6 − 2x now substitute: x − y = −3 x − (6 − 2x) = −3 university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 27. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Example: Solve the linear system by substitution: 2x + y = 6 x − y = −3 2x + y = 6 y = 6 − 2x now substitute: x − y = −3 x − (6 − 2x) = −3 3x − 6 = −3 university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 28. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Example: Solve the linear system by substitution: 2x + y = 6 x − y = −3 2x + y = 6 y = 6 − 2x now substitute: x − y = −3 x − (6 − 2x) = −3 3x − 6 = −3 x =1 university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 29. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Example: Solve the linear system by substitution: 2x + y = 6 x − y = −3 2x + y = 6 y = 6 − 2x now substitute: x − y = −3 x − (6 − 2x) = −3 3x − 6 = −3 x =1 Substituting we obtain y = 4. So, the solution is the point (1, 4). university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 30. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Graphing and substitution work well for systems involving two variables. university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 31. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Graphing and substitution work well for systems involving two variables. However, neither is easily extended to larger systems. university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 32. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Graphing and substitution work well for systems involving two variables. However, neither is easily extended to larger systems. Elimination by addition is the most important method of solution. university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 33. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Graphing and substitution work well for systems involving two variables. However, neither is easily extended to larger systems. Elimination by addition is the most important method of solution. It readily generalizes to larger systems and forms the basis for computer-based solution methods. university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 34. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Theorem (Operations that Produce Equivalent Systems) A system of linear equations is transformed into an equivalent system if university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 35. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Theorem (Operations that Produce Equivalent Systems) A system of linear equations is transformed into an equivalent system if (A) Two equations are interchanged. university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 36. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Theorem (Operations that Produce Equivalent Systems) A system of linear equations is transformed into an equivalent system if (A) Two equations are interchanged. (B) An equation is multiplied by a nonzero constant. university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 37. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Theorem (Operations that Produce Equivalent Systems) A system of linear equations is transformed into an equivalent system if (A) Two equations are interchanged. (B) An equation is multiplied by a nonzero constant. (C) A constant multiple of one equation is added to another equation. university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 38. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Example: Solve the linear system using elimination by addition 3u − 2v = 12 7u + 2v = 8 university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 39. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Example: Solve the linear system using elimination by addition 3u − 2v = 12 7u + 2v = 8 3u − 2v = 12 university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 40. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Example: Solve the linear system using elimination by addition 3u − 2v = 12 7u + 2v = 8 3u − 2v = 12 +7u + 2v = 8 university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 41. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Example: Solve the linear system using elimination by addition 3u − 2v = 12 7u + 2v = 8 3u − 2v = 12 +7u + 2v = 8 10u + 0 = 20 university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 42. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Example: Solve the linear system using elimination by addition 3u − 2v = 12 7u + 2v = 8 3u − 2v = 12 +7u + 2v = 8 10u + 0 = 20 u=2 university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 43. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Example: Solve the linear system using elimination by addition 3u − 2v = 12 7u + 2v = 8 3u − 2v = 12 +7u + 2v = 8 10u + 0 = 20 u=2 Substituting, we obtain v = −3. So the solution is (2,-3) university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 44. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Example: Solve using elimination by addition. 3x − 2y = 8 2x + 5y = −1 university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 45. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Example: Solve using elimination by addition. 3x − 2y = 8 2x + 5y = −1 We multiply the first equation by 5 and the bottom equation by 2 and then add. university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 46. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Example: Solve using elimination by addition. 3x − 2y = 8 2x + 5y = −1 We multiply the first equation by 5 and the bottom equation by 2 and then add. 15x − 10y = 40 university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 47. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Example: Solve using elimination by addition. 3x − 2y = 8 2x + 5y = −1 We multiply the first equation by 5 and the bottom equation by 2 and then add. 15x − 10y = 40 4x + 10y = −2 university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 48. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Example: Solve using elimination by addition. 3x − 2y = 8 2x + 5y = −1 We multiply the first equation by 5 and the bottom equation by 2 and then add. 15x − 10y = 40 4x + 10y = −2 19x = 38 university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 49. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Example: Solve using elimination by addition. 3x − 2y = 8 2x + 5y = −1 We multiply the first equation by 5 and the bottom equation by 2 and then add. 15x − 10y = 40 4x + 10y = −2 19x = 38 1 Now we multiply both sides of this last equation by 19 to obtain x = 2. university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 50. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Example: Solve using elimination by addition. 3x − 2y = 8 2x + 5y = −1 We multiply the first equation by 5 and the bottom equation by 2 and then add. 15x − 10y = 40 4x + 10y = −2 19x = 38 1 Now we multiply both sides of this last equation by 19 to obtain x = 2. Then we substitute back into either of the two original equations to obtain y = −1. university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 51. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Example: At $4.80 per bushel, the annual supply for soybeans in the Midwest is 1.9 billion bushels and the annual demand is 2.0 billion bushels. When the price increases to $5.10 per bushel, the annual supply increases to 2.1 billion bushels and the annual demand decreases to 1.8 billion bushels. Assume that the supply and demand equations are linear. university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 52. Systems in Two Variables Graphing Substitution Elimination by Addition Applications (a) Find the supply equation. university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 53. Systems in Two Variables Graphing Substitution Elimination by Addition Applications (a) Find the supply equation. We wish to find an equation of the form p = mq + b where p represents unit price and q represents quantity demanded. We have two points (q, p) on the graph of the supply equation: (1.9, 4.80) and (2.1, 5.10). university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 54. Systems in Two Variables Graphing Substitution Elimination by Addition Applications (a) Find the supply equation. We wish to find an equation of the form p = mq + b where p represents unit price and q represents quantity demanded. We have two points (q, p) on the graph of the supply equation: (1.9, 4.80) and (2.1, 5.10). The slope of this line is: university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 55. Systems in Two Variables Graphing Substitution Elimination by Addition Applications (a) Find the supply equation. We wish to find an equation of the form p = mq + b where p represents unit price and q represents quantity demanded. We have two points (q, p) on the graph of the supply equation: (1.9, 4.80) and (2.1, 5.10). The slope of this line is: 5.10 − 4.80 0.3 3 m= = = 2.1 − 1.9 0.2 2 university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 56. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Therefore the equation of this line is university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 57. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Therefore the equation of this line is 3 p − 4.8 = (q − 1.9) 2 university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 58. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Therefore the equation of this line is 3 p − 4.8 = (q − 1.9) 2 3 3 p = q − (1.9) + 4.8 2 2 university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 59. Systems in Two Variables Graphing Substitution Elimination by Addition Applications Therefore the equation of this line is 3 p − 4.8 = (q − 1.9) 2 3 3 p = q − (1.9) + 4.8 2 2 3 p = q + 1.95 2 university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 60. Systems in Two Variables Graphing Substitution Elimination by Addition Applications (b) Find the demand equation. university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 61. Systems in Two Variables Graphing Substitution Elimination by Addition Applications (b) Find the demand equation. Again, we want an equation of the form p = mq + b. We have two points on the graph of the demand equation: (2.0, 4.80) and (1.8, 5.10). university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 62. Systems in Two Variables Graphing Substitution Elimination by Addition Applications (b) Find the demand equation. Again, we want an equation of the form p = mq + b. We have two points on the graph of the demand equation: (2.0, 4.80) and (1.8, 5.10). The slope of this line is: 5.10 − 4.80 0.3 3 m= =− =− 1.8 − 2.0 0.2 2 university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 63. Systems in Two Variables Graphing Substitution Elimination by Addition Applications (b) Find the demand equation. Again, we want an equation of the form p = mq + b. We have two points on the graph of the demand equation: (2.0, 4.80) and (1.8, 5.10). The slope of this line is: 5.10 − 4.80 0.3 3 m= =− =− 1.8 − 2.0 0.2 2 Therefore the equation of this line is 3 p − 4.80 = − (q − 2.0) 2 university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 64. Systems in Two Variables Graphing Substitution Elimination by Addition Applications (b) Find the demand equation. Again, we want an equation of the form p = mq + b. We have two points on the graph of the demand equation: (2.0, 4.80) and (1.8, 5.10). The slope of this line is: 5.10 − 4.80 0.3 3 m= =− =− 1.8 − 2.0 0.2 2 Therefore the equation of this line is 3 p − 4.80 = − (q − 2.0) 2 3 3 p = − q + (2.0) + 4.80 2 2 university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 65. Systems in Two Variables Graphing Substitution Elimination by Addition Applications (b) Find the demand equation. Again, we want an equation of the form p = mq + b. We have two points on the graph of the demand equation: (2.0, 4.80) and (1.8, 5.10). The slope of this line is: 5.10 − 4.80 0.3 3 m= =− =− 1.8 − 2.0 0.2 2 Therefore the equation of this line is 3 p − 4.80 = − (q − 2.0) 2 3 3 p = − q + (2.0) + 4.80 2 2 3 p = − q + 7.80 university-logo 2 Jason Aubrey Math 1300 Finite Mathematics
  • 66. Systems in Two Variables Graphing Substitution Elimination by Addition Applications (c) Find the equilibrium price and quantity. university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 67. Systems in Two Variables Graphing Substitution Elimination by Addition Applications (c) Find the equilibrium price and quantity. We set supply equal to demand and solve: 3 3 − q + 7.80 = q + 1.95 2 2 university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 68. Systems in Two Variables Graphing Substitution Elimination by Addition Applications (c) Find the equilibrium price and quantity. We set supply equal to demand and solve: 3 3 − q + 7.80 = q + 1.95 2 2 3q = 5.85 university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 69. Systems in Two Variables Graphing Substitution Elimination by Addition Applications (c) Find the equilibrium price and quantity. We set supply equal to demand and solve: 3 3 − q + 7.80 = q + 1.95 2 2 3q = 5.85 q = 1.95 billion bushels university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 70. Systems in Two Variables Graphing Substitution Elimination by Addition Applications (c) Find the equilibrium price and quantity. We set supply equal to demand and solve: 3 3 − q + 7.80 = q + 1.95 2 2 3q = 5.85 q = 1.95 billion bushels Substituting, we find p = − 3 (1.95) + 7.80 = $4.88 2 university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 71. Systems in Two Variables Graphing Substitution Elimination by Addition Applications (d) Graph the two equations in the same coordinate system and identify the equilibrium point, supply curve, and demand curve. university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 72. Systems in Two Variables Graphing Substitution Elimination by Addition Applications f (d) Graph the two equations in the same coordinate system and identify the equilibrium point, supply curve, and demand curve. 6 4 2 0 2 4 6 8 10 12 university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 73. Systems in Two Variables Graphing Substitution Elimination by Addition Applications f (d) Graph the two equations in the same coordinate system and identify the equilibrium point, supply curve, and demand curve. 6 4 2 0 2 4 6 8 10 12 g university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 74. Systems in Two Variables Graphing Substitution Elimination by Addition Applications f (d) Graph the two equations in the same coordinate system and identify the equilibrium point, supply curve, and demand curve. 6 (1.95, 4.88) 4 2 0 2 4 6 8 10 12 g university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 75. Systems in Two Variables Graphing Substitution Elimination by Addition Applications f (d) Graph the two equations in the same coordinate system and identify the equilibrium point, supply curve, and demand curve. Supply Curve 6 (1.95, 4.88) 4 2 0 2 4 6 8 10 12 g university-logo Jason Aubrey Math 1300 Finite Mathematics
  • 76. Systems in Two Variables Graphing Substitution Elimination by Addition Applications f (d) Graph the two equations in the same coordinate system and identify the equilibrium point, supply curve, and demand curve. Supply Curve 6 (1.95, 4.88) 4 2 Demand Curve 0 2 4 6 8 10 12 g university-logo Jason Aubrey Math 1300 Finite Mathematics