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Ch 1 Final 10Math.pdf
1.
2. Chapter # 1
2
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UNIT # 1
QUADRATIC EQUATIONS
Ex # 1.1 Ex # 1.1
Quadratic equation Solving Quadratic equation by Factorization:
Introduction: In this method, a quadratic equation can easily be
solved by splitting it in factors.
The name Quadratic comes from “quad” means
square because the highest power of the variable
is 2.
Rules for Splitting:
𝐋𝐞𝐭 𝒂𝒙𝟐
+ 𝒃𝒙 + 𝒄 = 𝟎
Definition: 1. Write the quadratic equation in standard form if
necessary like above equation.
An equation in the form of 𝑎𝑥2
+ 𝑏𝑥 + 𝑐 = 0,
where 𝑎, 𝑏 and 𝑐 are real numbers and 𝑎 ≠ 0 2. First we find the product of 𝑎(coefficient of 𝑥2
)
and 𝑐 (constant term) i.e. 𝑎𝑐
OR
An equation of degree/ exponent/ power 2 is
called quadratic equation
3. Then find two numbers 𝑏1 and 𝑏2 such that
𝑏1 and 𝑏2 = 𝑏 and also 𝑏1𝑏2 = 𝑎. 𝑐
𝑎𝑥2
+ 𝑏𝑥 + 𝑐 = 0 is quadratic equation in one
variable.
4. Now 𝑎𝑥2
+ 𝑏1𝑥 + 𝑏2𝑥 + 𝑐 = 0 can be factorized
into two linear factors.
Solutions or Roots of equation: 5. Equate each factor to zero by zero – product
property.
All those values of the variable for which the
given equation is true are called solutions or
roots of the equation.
6. Solve the equation for given variable.
Example # 1 (i)
Solution Set: 𝟐𝒙𝟐
+ 𝟐𝒙 − 𝟏𝟏 = 𝟏
Solution:
2𝑥2
+ 2𝑥 − 11 = 1
2𝑥2
+ 2𝑥 − 11 − 1 = 0
2𝑥2
+ 2𝑥 − 12 = 0
2(𝑥2
+ 𝑥 − 6) = 0
𝑥2
+ 𝑥 − 6 = 0
𝑥2
+ 3𝑥 − 2𝑥 − 6 = 0
𝑥(𝑥 + 3) − 2(𝑥 + 3) = 0
𝑥 + 1 = 0 𝑜𝑟 𝑥 + 4 = 0
𝑥 = −1 𝑜𝑟 𝑥 = −4
𝐒𝐨𝐥𝐮𝐭𝐢𝐨𝐧 𝐒𝐞𝐭 = {−𝟏 , −𝟒}
The set of all solutions is called solution set.
Example:
𝒙𝟐
− 𝟗 = 𝟎
𝑥2
− 32
= 0
(𝑥 + 3)(𝑥 − 3) = 0
𝑥 + 3 = 0 𝑜𝑟 𝑥 − 3 = 0
𝑥 = −3 𝑜𝑟 𝑥 = 3
𝑥2
− 9 = 0 is true only for 𝑥 = 3 𝑎𝑛𝑑 𝑥 = −3,
Hence 𝑥 = 3 𝑎𝑛𝑑 𝑥 = −3 are the solutions or
roots of 𝑥2
− 9 = 0 and {3, −3} is the solution
set of 𝑥2
− 9 = 0
Note:
1. 𝑎𝑥2
+ 𝑏𝑥 + 𝑐 = 0 is called General or Standard
form of Quadratic equation.
2. In Quadratic equation 𝑎 ≠ 0
Methods of Solving Quadratic equation:
(a) By Factorization
(b) By Completing the Square
(c) By Quadratic Formula
3. Chapter # 1
3
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Example # 1 (ii) Ex # 1.1
𝟏𝟐𝐭𝟐
= 𝐭 + 𝟏 2. Solving Quadratic equation by Completing
square:
Solution:
12𝑡2
= 𝑡 + 1
12𝑡2
− 𝑡 − 1 = 0
12𝑡2
+ 3𝑡 − 4𝑡 − 1 = 0
3𝑡(4𝑡 + 1) − 1(4𝑡 + 1) = 0
(4𝑡 + 1)(3𝑡 − 1) = 0
4𝑡 + 1 = 0 𝑜𝑟 3𝑡 − 1 = 0
4𝑡 = −1 𝑜𝑟 3𝑡 = 1
𝑡 =
−1
4
𝑜𝑟 𝑡 =
1
3
1. Write the quadratic equation in its standard form
2. Divide all terms by the co-efficient of 𝑥2
if other
than 1
3. Shift the constant term to the right side of the
equation.
4. Multiply the co – efficient of 𝑥 with
1
2
then take
Square of it and Add to B.S
5. Write Left – hand side of the equation as a perfect
square and simplify the Right – hand side
6. Take square root on B.S of the equation and solve it.
Example # 2
A ball is thrown straight up, from 3 m above
the ground with a velocity of 14 m/s. When
does it hit the ground?
Example # 3
𝒙𝟐
− 𝟖𝒙 + 𝟗 = 𝟎
Solution:
Solution:
Height starts at 3 m = 3
Velocity is 14 m/s = 14t
𝑥2
− 8𝑥 + 9 = 0
Subtract 9 from B. S
𝑥2
− 8𝑥 + 9 − 9 = 0 − 9
𝑥2
− 8𝑥 = −9
Add (4)2
on B. S
𝑥2
− 8𝑥 + (4)2
= −9 + (4)2
Gravity pulls by 5𝑚/𝑠2
= −5𝑡2
The height h at any time t is:
ℎ = 3 + 14𝑡 − 5𝑡2
The height is zero when the ball hit the ground. (𝑥)2
− 2(𝑥)(4) + (4)2
= −9 + 16
0 = 3 + 14𝑡 − 5𝑡2
0 = −5𝑡2
+ 14𝑡 + 3
0 = −(5𝑡2
− 14𝑡 − 3)
0 = 5𝑡2
− 14𝑡 − 3
5𝑡2
− 14𝑡 − 3 = 0
5𝑡2
+ 1𝑡 − 15𝑡 − 3 = 0
𝑡(5𝑡 + 1) − 3(5𝑡 + 1) = 0
(5𝑡 + 1)(𝑡 − 3) = 0
5𝑡 + 1 = 0 𝑜𝑟 𝑡 − 3 = 0
5𝑡 = −1 𝑜𝑟 𝑡 = 3
𝑡 =
−1
5
𝑜𝑟 𝑡 = 3
The 𝑡 =
−1
5
is negative time which is impossible
(𝑥 − 4)2
= 7
√(𝑥 − 4)2 = ±√7
𝑥 − 4 = ±√7
𝑥 = 4 ± √7
3. Solving Quadratic equation by Quadratic
Formula:
1. Write the quadratic equation in its standard form:
2. Compare the given equation with the standard
quadratic equation 𝑎𝑥2
+ 𝑏𝑥 + 𝑐 = 0 to get the
values of 𝑎, b and c.
3. Put the values of 𝑎, b and c in the given formula.
𝑥 =
−𝑏 ± √𝑏2 − 4𝑎𝑐
2𝑎
So the ball hits the ground after 3 seconds.
4. Now solve it for the values of variable.
Note:
By Quadrating formula we can solve all quadratic
equations.
4. Chapter # 1
4
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Ex # 1.1 Ex # 1.1
Derivation of Quadratic Formula:
𝑥 =
−(−6) ± √(−6)2 − 4(3)(2)
2(3)
𝑥 =
6 ± √36 − 24
6
𝑥 =
6 ± √12
6
𝑥 =
6 ± √4 × 3
6
𝑥 =
6 ± 2√3
6
𝑥 =
2(3 ± √3)
6
𝑥 =
3 ± √3
3
𝑥 =
3
3
±
√3
3
𝑥 = 1 ±
√3
3
𝐒𝐨𝐥𝐮𝐭𝐢𝐨𝐧 𝐒𝐞𝐭 = {1 ±
√3
3
}
As we have standard form of quadratic equation:
𝑎𝑥2
+ 𝑏𝑥 + 𝑐 = 0
Divide each term by "𝑎"
𝑎𝑥2
𝑎
+
𝑏𝑥
𝑎
+
𝑐
𝑎
=
0
𝑎
𝑥2
+
𝑏𝑥
𝑎
+
𝑐
𝑎
= 0
Shift the constant term
𝑐
𝑎
to right side
𝑏
𝑎
×
1
2
=
𝑏
2𝑎
𝑥2
+
𝑏𝑥
𝑎
= −
𝑐
𝑎
Add (
𝑏
2𝑎
)
2
𝑜𝑓 𝐵. 𝑆
𝑥2
+
𝑏𝑥
𝑎
+ (
𝑏
2𝑎
)
2
= (
𝑏
2𝑎
)
2
−
𝑐
𝑎
(𝑥)2
+ 2(𝑥) (
𝑏
2𝑎
) + (
𝑏
2𝑎
)
2
=
𝑏2
4𝑎2
−
𝑐
𝑎
(𝑥 +
𝑏
2𝑎
)
2
=
𝑏2
− 4𝑎
4𝑎2
√(𝑥 +
𝑏
2𝑎
)
2
= ±√
𝑏2 − 4𝑎𝑐
4𝑎2
𝑥 +
𝑏
2𝑎
= ±
√𝑏2 − 4𝑎𝑐
√4𝑎2
𝑥 +
𝑏
2𝑎
= ±
√𝑏2 − 4𝑎𝑐
2𝑎
𝑥 =
−𝑏
2𝑎
±
√𝑏2 − 4𝑎𝑐
2𝑎
𝑥 =
− 𝑏 ± √𝑏2 − 4𝑎𝑐
2𝑎
Example # 5
A company is making frames of a new product
they are launching. The frame will be cut out of
a piece of steel. To keep the weight down, the
final area should be 28 𝒄𝒎𝟐
. The inside of the
frame has to be 11 cm by 6 cm. what should the
width 𝒙 of the meatal be?
Solution:
According to condition:
Length = 11 + 2𝑥
Width = 6 + 2𝑥
Area of steel before cutting
𝐴𝑟𝑒𝑎 = (11 + 2𝑥)(6 + 2𝑥)
𝐴𝑟𝑒𝑎 = 66 + 22𝑥 + 12𝑥 + 4𝑥2
𝐴𝑟𝑒𝑎 = 66 + 34𝑥 + 4𝑥2
𝐴𝑟𝑒𝑎 = 4𝑥2
+ 34𝑥 + 66
Area of steel after cutting out the 11 × 6 middle
𝐴𝑟𝑒𝑎 = 4𝑥2
+ 34𝑥 + 66 − 11 × 6
𝐴𝑟𝑒𝑎 = 4𝑥2
+ 34𝑥
As Area is 28 𝑐𝑚2
28 = 4𝑥2
+ 34𝑥
0 = 4𝑥2
+ 34𝑥 − 28
4𝑥2
+ 34𝑥 − 28 = 0
2(2𝑥2
+ 17𝑥 − 14) = 0
Example # 4
Solve 𝟑𝒙𝟐
− 𝟔𝒙 + 𝟐 = 𝟎 by quadratic formula.
Solution:
3𝑥2
− 6𝑥 + 2 = 0
Compare it with 𝑎𝑥2
+ 𝑏𝑥 + 𝑐 = 0
Here 𝑎 = 3, 𝑏 = −6, 𝑐 = 2
As we have
𝑥 =
−𝑏 ± √𝑏2 − 4𝑎𝑐
2𝑎
Put the values