Weitere Γ€hnliche Inhalte Γhnlich wie Task compilation - Differential Equation II (20) Mehr von Jazz Michele Pasaribu (8) KΓΌrzlich hochgeladen (20) Task compilation - Differential Equation II2. TASK I (February, 13th 2014)
Determine the solution of::
1.
π2 π¦
ππ‘2
β 2
ππ¦
ππ‘
β 5π¦ = 0, y(0)=0; yβ(0)=1
2.
π2 π¦
ππ‘2
β 3
ππ¦
ππ‘
= 0, y(0)=0; yβ(0)=1
3.
π2 π¦
ππ‘2
β 4
ππ¦
ππ‘
β 4π¦ = 0, y(0)=0; yβ(0)=1
Solution:
1.
π2 π¦
ππ‘2 β 2
ππ¦
ππ‘
β 5π¦ = 0, y(0)=0; yβ(0)=1
Characteristic Equation: π2
β 2π β 5 = 0
π1,2 =
βπ Β± βπ2 β 4ππ
2π
=
β(β2) Β± β(β2)2 β 4(1)(β5)
2(1)
=
2 Β± β4 + 20
2
=
2 Β± β24
2
=
2 Β± 2β6
2
= 1 Β± β6
π1and π2 are real and distinct, then π¦ = π1 π π1 π₯
+ π2 π π2 π₯
π¦(0) = 0
0 = π1 + π2
π1 = βπ2 .................... (1)
π¦β²(0) = 1
π¦β²(π₯) = (1 + β6)π1 π(1+β6)π₯
+ (1 β β6)π1 π(1ββ6)π₯
1 = (1 + β6)π1 + (1 β β6)π2
1 = (1 + β6)π1 + (1 β β6)(βπ1)
1 = π1(1 + β6 β 1 + β6)
1 = 2β6π1
π1 =
1
12
β6
3. π1 = βπ2 .................... (1)
π2 = β
1
12
β6
Maka, π¦ =
1
12
β6π(1+β6)π₯
β
1
12
β6π(1ββ6)π₯
2.
π2 π¦
ππ‘2
β 3
ππ¦
ππ‘
= 0, y(0)=0; yβ(0)=1
Characteristic Equation:π2
β 3π = 0
π(π β 3) = 0
π1 = 0 β¨ π2 = 3
π1and π2 are real and distinct, then π¦ = π1 π π1 π₯
+ π2 π π2 π₯
π¦ = π1 π0π₯
+ π2 π3π₯
π¦(0) = 0
0 = π1 + π2
π1 = βπ2 .................... (1)
π¦β²(0) = 1
π¦β²(π₯) = 3π2
3π₯
1 = 3π2
π2 =
1
3
π1 = β
1
3
Then, π¦ = β
1
3
π π1 π₯
+
1
3
π π2 π₯
3.
π2 π¦
ππ‘2
β 4
ππ¦
ππ‘
β 4π¦ = 0, y(0)=0; yβ(0)=1
Characteristic Equation:π2
β 4π β 4 = 0
π1,2 =
βπ Β± βπ2 β 4ππ
2π
=
β(β4) Β± β(β4)2 β 4(1)(β4)
2(1)
=
4 Β± β16 + 16
2
=
4 Β± 4β2
2
= 2 Β± 2β2
4. π1and π2 are real and distinct, then π¦ = π1 π π1 π₯
+ π2 π π2 π₯
π¦ = π1 π(2+2β2)π₯
+ π2 π(2β2β2)π₯
π¦(0) = 0
0 = π1 + π2
π1 = βπ2 .................... (1)
π¦β²(0) = 1
π¦β²(π₯) = (2 + 2β2)π1 π(2+2β2)π₯
+ (2 β 2β2)π2 π(2β2β2)π₯
1 = (2 + 2β2)π1 + (2 β 2β2)π2
1 = (2 + 2β2)π1 + (2 β 2β2)(βπ1)
1 = π1(2 + 2β2 β 2 + 2β2)
1 = π1(4β2)
π1 =
1
8
β2
π1 = βπ2 .................... (1)
π2 = β
1
8
β2
Maka,
π¦ =
1
8
β2π(2+2β2)π₯
β
1
8
β2π(2β2β2)π₯
5. TASK II (February, 20th 2014)
Solve these equation:
1.
π4 π¦
ππ₯4
+ 10
π2 π¦
ππ₯2
+ 9π¦ = 0
2.
π4 π¦
ππ₯4 +
π3 π¦
ππ₯3 +
π2 π¦
ππ₯2 + 2π¦ = 0
3. π¦β²β²β²
+ 4π¦β²
= 0
4. π¦(4)
+ 4π¦β²β²
β π¦β²
+ 6π¦ = 0
5.
π6 π¦
ππ₯6
β 4
π5 π¦
ππ₯5
+ 16
π4 π¦
ππ₯4
β 12
π3 π¦
ππ₯3
+ 41
π2 π¦
ππ₯2
β 8
ππ¦
ππ₯
+ 26π¦ = 0
Solution:
1.
π4 π¦
ππ₯4
+ 10
π2 π¦
ππ₯2
+ 9π¦ = 0
Characteristic equation: π4
+ 10π2
+ 9 = 0
(π2
+ 9)(π2
+ 1) = 0
(π + 3π)(π β 3π)(π + π)(π β π) = 0
π1 = β3π β π2 = β3π β π3 = βπ β π3 = π
So, the solution is π¦ = πΆ1 cos 3π₯ + πΆ2 sin 3π₯ + πΆ3 cos π₯ + πΆ4 sin π₯
2.
π4 π¦
ππ₯4
+
π3 π¦
ππ₯3
+
π2 π¦
ππ₯2
+ 2π¦ = 0
Characteristic equation: π4
+ π3
+ π2
+ 2 = 0
(π2
β π + 1)(π2
+ 2π + 2) = 0
ο· (π2
β π + 1) = 0
π1,2 =
βπ Β± βπ2 β 4ππ
2π
π1,2 =
β(β1) Β± β(β1)2 β 4(1)(1)
2(1)
π1,2 =
1 Β± β1 β 4
2
π1,2 =
1 Β± β3π
2
π1 =
1
2
+
1
2
β3π and π2 =
1
2
β
1
2
β3π
ο· (π2
+ 2π + 2) = 0
π3,4 =
βπ Β± βπ2 β 4ππ
2π
6. π3,4 =
β(2) Β± β(2)2 β 4(1)(2)
2(1)
π3,4 =
β2 Β± β4 β 8
2
π3,4 =
β2 Β± 2π
2
π3 = β1 + π and π4 = β1 β π
So, the solution is π¦ = π
1
2
π₯
(πΆ1 cos
1
2
β3π₯ + πΆ2 sin
1
2
β3π₯) + πβπ₯
(πΆ3 cos π₯ +
πΆ4 sin π₯)
3. π¦β²β²β²
+ 4π¦β²
= 0
Characteristic equation: π3
+ 4π = 0
π(π2
+ 4) = 0
π(π + 2π)(π β 2π) = 0
π1 = 0 β π2 = β2π β π3 = 2π
So, the solution is π¦ = πΆ1 + πΆ2cos2π₯ + πΆ3 sin 2π₯
4. π¦(4)
+ 4π¦β²β²
β π¦β²
+ 6π¦ = 0
Characteristics equation is π4
+ 4π2
β π + 6 = 0
(π2
β π + 2)(π2
+ π + 3) = 0
ο· (π2
β π + 2) = 0
π1,2 =
βπ Β± βπ2 β 4ππ
2π
π1,2 =
β(β1) Β± β(β1)2 β 4(1)(2)
2(1)
π1,2 =
1 Β± β1 β 8
2
π1,2 =
1 Β± β7π
2
π1 =
1
2
+
1
2
β7π and π2 =
1
2
β
1
2
β7π
ο· (π2
+ π + 3) = 0
π3,4 =
βπ Β± βπ2 β 4ππ
2π
π3,4 =
β(1) Β± β(1)2 β 4(1)(3)
2(1)
7. π3,4 =
β1 Β± β1 β 12
2
π3,4 =
β1 Β± β11π
2
π3 = β
1
2
+
1
2
β11π and π4 = β
1
2
β
1
2
β11π
So, the equation is:
π¦ = π
1
2
π₯
(πΆ1 cos
1
2
β7π₯ + πΆ2 sin
1
2
β7π₯) + πβ
1
2
π₯
(πΆ3 cos
1
2
β11 π₯ + πΆ4 sin
1
2
β11 π₯)
5.
π6 π¦
ππ₯6
β 4
π5 π¦
ππ₯5
+ 16
π4 π¦
ππ₯4
β 12
π3 π¦
ππ₯3
+ 41
π2 π¦
ππ₯2
β 8
ππ¦
ππ₯
+ 26π¦ = 0
Characteristic equation is π6
β 4π5
+ 16π4
β 12π3
+ 41π2
β 8π + 26 = 0
(π4
+ 3π2
+ 2)(π2
β 4π + 13) = 0
(π2
+ 1)(π2
+ 2)(π2
β 4π + 13) = 0
ο· (π2
+ 1) = 0
π1,2 =
βπ Β± βπ2 β 4ππ
2π
π1,2 =
0 Β± β0 β 4(1)(1)
2(1)
π1,2 =
Β±ββ4
2
π1,2 =
Β±2π
2
π1 = π and π2 = βπ
ο· (π2
+ 2) = 0
π3,4 =
βπ Β± βπ2 β 4ππ
2π
π3,4 =
0 Β± β0 β 4(1)(2)
2(1)
8. π3,4 =
Β±ββ8
2
π3,4 =
Β±2β2π
2
π3 = β2π and π4 = ββ2π
ο· (π2
β 4π + 13) = 0
π5,6 =
βπ Β± βπ2 β 4ππ
2π
π5,6 =
β(β4) Β± β(β4)2 β 4(1)(13)
2(1)
π5,6 =
4 Β± β16 β 52
2
π5,6 =
4 Β± 6π
2
π5 = 2 + 3π and π6 = 2 β 3π
So, the solution is π¦ = πΆ1 cos π₯ + πΆ1 sin π₯ + π2π₯(πΆ3 cos 3π₯ + πΆ4 sin 3π₯) +
πΆ5 cos β2π₯ + πΆ5 sin β2π₯
9. TASK III (March 7th, 2014)
1.
π3 π
ππ‘3
β 5
π2 π
ππ‘2
+ 25
ππ
ππ‘
β 125π = β60π7π‘
y(0)=0, yβ(0)=1, yβ(0)=2
2. π¦(πΌπ)
β 6π¦β²β²β²
+ 16π¦β²β²
+ 54π¦β²
β 225π¦ = 100πβ2π₯
π¦(0) = π¦β²(0) = π¦β²β²(0) = π¦β²β²β²(0) = 1
Solution:
1.
π3 π
ππ‘3 β 5
π2 π
ππ‘2 + 25
ππ
ππ‘
β 125π = β60π7π‘
y(0)=0, yβ(0)=1, yβ(0)=2
Quadratic equation: π3
β 5π2
+ 25π β 125 = β60π7π‘
Y= yl + yr
π3
β 5π2
+ 25π β 125 = 0
(π β 5)(π + 5π)(π β 5π) = 0
π¦π = π1 π5π‘
+ π2 cos 5π‘ + π3 sin 5π‘
π¦π = π΄0 π7π‘
π¦π
β²
= 7π΄0 π7π‘
π¦π
β²β²
= 49π΄0 π7π‘
π¦π
β²β²β²
= 343π΄0 π7π‘
π¦β²β²β²
β 5π¦β²β²
+ 25π¦ β 125π¦ = β60π7π‘
343π΄0 π7π‘
β 245π΄0 π7π‘
+ 175π΄0 π7π‘
β 125π΄0 π7π‘
= β60π7π‘
148π΄0 π7π‘
= β60π7π‘
π΄0 = β
60
148
= β
15
37
π¦π = β
15
37
π7π‘
10. Then, we got the equation is equal to
Y= yl + yr
π¦(π‘) = π1 π5π‘
+ π2 cos 5π‘ + π3 sin 5π‘ β
15
37
π7π‘
Now, we are going to find the value of c1, c2, and c3.
y(0)=0
0 = π1 + π2 β
15
37
π1 + π2 =
15
37
........................................ (1)
yβ(0)=1
π¦β²
(π‘) = 5π1 π5π‘
β 5π2 sin 5π‘ + 5π3 cos 5π‘ β
105
37
π7π‘
1 = 5π1 + 5π3 β
105
37
π1 + π3 =
142
185
.................................... (2)
yβ(0)=2
π¦β²β²
(π‘) = 25π1 π5π‘
β 25π2 cos 5π‘ β 25π3 sin 5π‘ β
735
37
π7π‘
2 = 25π1 β 25π2 β
735
37
25π1 β 25π2 =
809
37
π1 β π2 =
809
925
....................................... (3)
Elimination of π2 from (1) and (3)
π1 β π2 =
809
925
....................................... (3)
π1 + π2 =
15
37
........................................ (1)
2π1 =
809 + 375
925
π1 =
592
925
From (3), we can get the value of c2 by substituting the value of c1.
π1 β π2 =
809
925
....................................... (3)
+
11. 592
925
β π2 =
809
925
π2 = β
217
925
From (2), we can get the value of c3 by substituting the value of c1.
π1 + π3 =
142
185
.................................... (2)
592
925
+ π3 =
142
185
π3 =
118
925
After getting the value of c1, c2, and c3, then the equation is:
π¦(π‘) =
592
925
π5π‘
β
217
925
cos 5π‘ +
118
925
sin 5π‘ β
15
37
π7π‘
2. π¦(πΌπ)
β 6π¦β²β²β²
+ 16π¦β²β²
+ 54π¦β²
β 225π¦ = 100πβ2π₯
π¦(0) = π¦β²(0) = π¦β²β²(0) = π¦β²β²β²(0) = 1
Quadratic equation: π4
β 6π3
+ 16π2
+ 54π β 225 = 100πβ2π₯
π¦ = π¦π + π¦π
π4
β 6π3
+ 16π2
+ 54π β 225 = 0
By using Horner method and ABC formula, so that the roots are gotten:
π1 = 3 π3 = 3 + 4π
π2 = β3 π4 = 3 β 4π
π¦π = π1 π3π‘
+ π2 πβ3π‘
+ π3π‘
(π3 cos 4π‘ + π4 sin 4π‘)
π¦π = π΄0 πβ2π₯
π¦π
β²
= β2π΄0 πβ2π‘
12. π¦π
β²β²
= 4π΄0 πβ2π‘
π¦π
β²β²β²
= β8π΄0 πβ2π‘
π¦π
(πΌπ)
= 16π΄0 πβ2π‘
π¦(πΌπ)
β 6π¦β²β²β²
+ 16π¦β²β²
+ 54π¦β²
β 225π¦ = 100πβ2π‘
16π΄0 πβ2π‘
+ 48π΄0 πβ2π‘
+ 64π΄0 πβ2π‘
β 108π΄0 πβ2π‘
β 225π΄0 πβ2π‘
= 100πβ2π‘
β205π΄0 πβ2π‘
= 100πβ2π‘
π΄0 = β
100
205
= β
20
41
So, the value of yr is
π¦π = β
20
41
πβ2π‘
π¦ = π1 π3π‘
+ π2 πβ3π‘
+ π3π‘
(π3 cos 4π‘ + π4 sin 4π‘) β
20
41
πβ2π‘
Now, we are going to find the value of c1, c2, and c3.
y(0) = 1
1 = π1 + π2 + π3 β
20
41
π1 + π2 + π3 =
61
41
....................................... (1)
yβ(0)=1
π¦β²
= 3π1 π3π‘
β 3π2 πβ3π‘
+ 3π3π‘(π3 cos 4π‘ + π4 sin 4π‘) + π3π‘(β4π3 sin 4π‘ + 4π4 cos 4π‘)
+
40
41
πβ2π‘
1 = 3π1 β 3π2 + 3π3 + 4π4 +
40
41
3π1 β 3π2 + 3π3 + 4π4 =
1
41
........................ (2)
yββ(0)=1
13. π¦β²β²
= 9π1 π3π‘
+ 9π2 πβ3π‘
+ 9π3π‘(π3 cos 4π‘ + π4 sin 4π‘) + 3π3π‘(β4π3 sin 4π‘ + 4π4 cos 4π‘) +
3π3π‘(β4π3 sin 4π‘ + 4π4 cos 4π‘) β 16π3π‘(π3 cos 4π‘ + π4 sin 4π‘) +
80
41
πβ2π‘
1 = 9π1 + 9π2 + 9π3 + 12π4 + 12π4 β 16π3 β
80
41
1 = 9(π1 + π2 + π3) + 24π4 β 16π3 β
80
41
121
41
= 9(
61
41
) + 24π4 β 16π3
β
428
41
= 24π4 β 16π3
2π3 β 3π4 =
107
82
.......................................... (3)
yβββ(0)=1
π¦β²β²β²
= 27π1 π3π‘
β 27π2 πβ3π‘
+ 75π3π‘(π3 cos 4π‘ + π4 sin 4π‘) β 100π3π‘(βπ3 sin 4π‘ +
π4 cos 4π‘) +
160
41
πβ2π‘
1 = 27π1 β 27π2 + 75π3 β 100π4 +
160
41
27π1 β 27π2 + 75π3 β 100π4 = β
119
41
........ (4)
To get the value of c1, c2, c3, and c4, we can use elimination and substituion method from the
above equations.
From (4) and (2), we can get the new equation:
27π1 β 27π2 + 75π3 β 100π4 = β
119
41
........ (4)
27π1 β 27π2 + 27π3 + 36π4 =
9
41
................ (2)
43π3 β 136π4 = β
128
41
6π3 β 176π4 = β
16
41
..................................... (5)
From (5) and (3), we can get the value of c4.
+
14. 6π3 β 176π4 = β
16
41
..................................... (5)
6π3 β 9π4 =
321
82
... ....................................... (3)
β8π4 =
β32 β 321
82
π4 =
β353
656
From (3), we can get the value of c3.
2π3 β 3(
β353
656
) =
107
82
.......................................... (3)
2π3 =
1915
656
π3 =
1915
1315
From (1), we get:
π1 + π2 +
1915
1315
=
61
41
....................................... (1)
π1 + π2 =
37
1312
................................................ (6)
From (2), we get:
3π1 β 3π2 + 3(
1915
1315
) + 4(
β353
656
) =
1
41
........................ (2)
3π1 β 3π2 =
32 β 5745 β 2824
1312
3π1 β 3π2 = β
8537
1312
π1 β π2 = β
8537
3936
................................................ (7)
From (6) and (7), we can get the value of c1 and c2 by elimination method.
π1 + π2 =
37
1312
................................................ (6)
+
15. π1 β π2 = β
8537
3936
............................................. (7)
2π1 =
β8537 + 111
3936
2π1 =
β8426
3936
π1 =
β4213
3936
From (7), we can get the value of c2.
β4213
3936
β π2 = β
8537
3936
............................................. (7)
π2 =
8537 β 4213
3936
π2 =
1081
656
After getting the value of c1, c2, c3, and c4, we get the characteristic value.
π¦ = β
4213
3936
π3π‘
+
1081
656
πβ3π‘
+ π3π‘
(
1915
1315
cos 4π‘ β
353
656
sin 4π‘) β
20
41
πβ2π‘
+
16. TASK IV (March 13th, 2014)
1.
π2 π
ππ‘2
+ 1000
ππ
ππ‘
+ 25000π = 24
π(0) = πβ²(0) = 0
2.
π2 π¦
ππ‘2
β 4
ππ¦
ππ‘
+ π¦ = 2π‘3
+ 3π‘2
β 1
π¦(0) = π¦β²(0) = 1
Solution:
1. πβ²β² + 1000πβ² + 25000π = 24
Quadratic equation:
π‘2
+ 1000π‘ + 25000 = 0
π‘1,2 =
βπ Β± βπ2 β 4ππ
2π
π‘1,2 =
β1000 Β± β(1000)2 β 4(1)(25000)
2(1)
π‘1,2 =
β1000 Β± β900000
2
π‘1,2 =
β1000 Β± 300β10
2
π‘1,2 = β500 Β± 150β10
π‘1 = β500 + 150β10 and π‘2 = β500 β 150β10
ππ = π1 π(β500+150β10)π‘
+ π2 π(β500β150β10)π‘
π π = π΄0
πβ² π = 0
πβ²β² π = 0
πβ²β² + 1000πβ² + 25000π = 24
0 + 1000(0) + 25000(π΄0) = 24
π΄0 =
3
3125
, then
π π =
3
3125
17. π = ππ + π π
π(π‘) = π1 π(β500+150β10)π‘
+ π2 π(β500β150β10)π‘
+
3
3125
π(0) = 0
0 = π1 + π2 +
3
3125
π1 + π2 = β
3
3125
...................................(1)
πβ²(π‘) = (β500 + 150β10)π1 π(β500+150β10)π‘
+ (β500 β 150β10)π2 π(β500β150β10)π‘
πβ²(0) = 0
0 = (β500 + 150β10)π1 + (β500 β 150β10)π2 ........................... (2)
By using elimination method, we can find the value of c1 from (1) and (2).
(β500 β 150β10)π1 + (β500 β 150β10)π2 = β
3
3125
(β500 β 150β10)
(β500 + 150β10)π1 + (β500 β 150β10)π2 = 0
β300β10π1 = β
3
3125
(β500 β 150β10)
π1 =
β5β10 β 15
3125
By using (1), we can find the value of c2.
π1 + π2 = β
3
3125
β5β10 β 15
3125
+ π2 = β
3
3125
π2 =
5β10 + 12
3125
After finding the value of c1 and c2, we get the equation.
π(π‘) = (
β5β10 β 15
3125
) π(β500+150β10)π‘
+ (
5β10 + 12
3125
) π(β500β150β10)π‘
+
3
3125
β
18. 2. π¦β²β² β 4π¦β² + π¦ = 2π‘3
+ 3π‘2
β 1
Quadratic equation:
π‘2
β 4π‘ + 1 = 0
π‘1,2 =
βπ Β± βπ2 β 4ππ
2π
π‘1,2 =
β(β4) Β± β(β4)2 β 4(1)(1)
2(1)
π‘1,2 =
4 Β± β12
2
π‘1,2 =
4 Β± 2β3
2
π‘1,2 = 2 Β± β3
π‘1 = 2 + β3 and π‘2 = 2 β β3
π¦π = π1 π(2+β3)π‘
+ π2 π(2ββ3)π‘
π¦π = π΄3 π‘3
+ π΄2 π‘2
+ π΄1 π‘ + π΄0
π¦β² π = 3π΄3 π‘2
+ 2π΄2 π‘ + π΄1
π¦β²β² π = 6π΄3 π‘ + 2π΄2
π¦β²β² β 4π¦β² + π¦ = 2π‘3
+ 3π‘2
β 1
(6π΄3 π‘ + 2π΄2) β 4(3π΄3 π‘2
+ 2π΄2 π‘ + π΄1) + (π΄3 π‘3
+ π΄2 π‘2
+ π΄1 π‘ + π΄0) = 2π‘3
+ 3π‘2
β 1
π΄3 π‘3
+ (β12π΄3 + π΄2)π‘2
+ (6π΄3 β 8π΄2 + π΄1)π‘ + π΄1 + π΄0 = 2π‘3
+ 3π‘2
β 1
Equation similarity:
π΄3 = 2
β12π΄3 + π΄2 = 3
β12(2) + π΄2 = 3
π΄2 = 27
6π΄3 β 8π΄2 + π΄1 = 0
6(2) β 8(27) + π΄1 = 0
π΄1 = 204
19. π΄1 + π΄0 = β1
204 + π΄0 = β1
π΄0 = β205
π¦π = 2π‘3
+ 27π‘2
+ 204π‘ β 205
π¦ = π¦π + π¦π
π¦(π‘) = π1 π(2+β3)π‘
+ π2 π(2ββ3)π‘
+ 2π‘3
+ 27π‘2
+ 204π‘ β 205
π¦(0) = 1
1 = π1 + π2 β 205
π1 + π2 = 206 .........................(1)
π¦β²(π‘) = (2 + β3)π1 π(2+β3)π‘
+ (2 β β3)π2 π(2ββ3)π‘
+ 6π‘2
+ 54π‘ + 204
π¦β²(0) = 1
1 = (2 + β3)π1 + (2 β β3)π2 + 204
(2 + β3)π1 + (2 β β3)π2 = β203 ........................... (2)
By using elimination and substitution method, the value of c1 and c2 can be obtained
from (1) and (2).
β203 = (2 + β3)π1 + (2 β β3)π2........................... (2)
206 = (2 β β3)π1 + (2 β β3)π2 ...................................(1)
2β3π1 = β203 β 206(2 β β3)
2β3π1 = β715 + 206β3
π1 =
β715β3 + 618
6
π1 + π2 = 206
(
β715β3 + 618
6
) + π2 = 206
π2 =
715β3 + 618
6
π¦(π‘) = (
β715β3+618
6
) π(2+β3)π‘
+ (
715β3+618
6
) π(2ββ3)π‘
+ 2π‘3
+ 27π‘2
+ 204π‘ β 205
β
20. TASK V (March 20th, 2014)
1.
π2 π₯
ππ‘2
+ 4
ππ₯
ππ‘
+ 8π₯ = (20π‘2
+ 16π‘ β 78)π2π‘
y(0)=yβ(0)=0
2.
π3 π
ππ‘3 β 5
π2 π
ππ‘2 + 25
ππ
ππ‘
β 125π = (β500π‘2
+ 465π‘ β 387)π2π‘
q(0)=qβ(0)= qββ(0)=0
Solution:
1.
π2 π₯
ππ‘2
+ 4
ππ₯
ππ‘
+ 8π₯ = (20π‘2
+ 16π‘ β 78)π2π‘
y(0)=yβ(0)=0
quadratic equation is
π2
+ 4π + 8 = 0
π1,2 =
βπ Β± βπ2 β 4ππ
2π
π1,2 =
β4 Β± β42 β 4(1)(8)
2(1)
π1,2 =
β4 Β± ββ16
2
π1,2 = β2 Β± 2π
π¦π = πβ2π‘
(π1 cos 2π‘ + π2 sin 2π‘)
π¦π = (π΄2 π‘2
+ π΄1 π‘ + π΄0)π2π‘
π¦β² π = (2π΄2 π‘ + π΄1)π2π‘
+ (π΄2 π‘2
+ π΄1 π‘ + π΄0)(2π2π‘)
π¦β²β² π = 2π΄2 π2π‘
+ (2π΄2 π‘ + π΄1)(2π2π‘) + (2π΄2 π‘ + π΄1)(2π2π‘) + (π΄2 π‘2
+ π΄1 π‘ + π΄0)(4π2π‘)
π¦β²β²
+ 4π¦β² + 8π¦ = (20π‘2
+ 16π‘ β 78)π2π‘
2π΄2 π2π‘
+ (2π΄2 π‘ + π΄1)(2π2π‘) + (2π΄2 π‘ + π΄1)(2π2π‘) + (π΄2 π‘2
+ π΄1 π‘ + π΄0)(4π2π‘) +
4{(2π΄2 π‘ + π΄1)π2π‘
+ (π΄2 π‘2
+ π΄1 π‘ + π΄0)(2π2π‘)} + 8{(π΄2 π‘2
+ π΄1 π‘ + π΄0)π2π‘} = (20π‘2
+
16π‘ β 78)π2π‘
(2π΄2 + 8π΄1 + 20π΄0)π2π‘
+ (16π΄2 + 20π΄1)π‘π2π‘
+ (20π΄2)π‘2
π2π‘
= (20π‘2
+ 16π‘ β
78)π2π‘
ο· 20π΄2 = 20
π΄2 = 1
21. ο· 16π΄2 + 20π΄1 = 16
16(1) + 20π΄1 = 16
20π΄1 = 0
π΄1 = 0
ο· 2π΄2 + 8π΄1 + 20π΄0 = β78
2(1) + 8(0) + 20π΄0 = β78
20π΄0 = β78 β 2
20π΄0 = β80
π΄0 = β4
π¦π = (π‘2
β 4)π2π‘
y = yl + yr
π¦(π‘) = πβ2π‘(π1 cos 2π‘ + π2 sin 2π‘) + (π‘2
β 4)π2π‘
π¦β²(π‘)
= (β2πβ2π‘)(π1 cos 2π‘ + π2 sin 2π‘) + πβ2π‘(β2π1 sin 2π‘ + 2π2 cos 2π‘) + 2π‘π2π‘
+
(π‘2
β 4)(2π2π‘)
π¦(0) = 0
0 = π1 β 4
π1 = 4
π¦β²(0) = 0
0 = β2π1 + 2π2 β 8
8 = β2(4) + 2π2
π2 = 8
π¦(π‘) = πβ2π‘(4 cos 2π‘ + 8 sin 2π‘) + (π‘2
β 4)π2π‘
2.
π3 π
ππ‘3
β 5
π2 π
ππ‘2
+ 25
ππ
ππ‘
β 125π = (β500π‘2
+ 465π‘ β 387)π2π‘
q(0)=qβ(0)= qββ(0)=0
Quadratic equation is:
π3
β 5π2
+ 25π β 125 = 0
22. π1 = 5
π2 = 5π
π3 = β5π
π¦π = π1 π5π‘
+ π2 cos 5π‘ + π3 sin 5π‘
π¦π = (π΄2 π‘2
+ π΄1 π‘ + π΄0)π2π‘
π¦β²
π
= (2π΄2 π‘ + π΄1)π2π‘
+ (π΄2 π‘2
+ π΄1 π‘ + π΄0)(2π2π‘
)
= 2π΄2 π‘π2π‘
+ π΄1 π2π‘
+ 2π΄2 π‘2
π2π‘
+ 2π΄1 π‘π2π‘
+ 2π΄0 π2π‘
π¦β²β²
π
= 2π΄2 π2π‘
+ 8π΄2 π‘π2π‘
+ 2π΄1 π2π‘
+ 4π΄2 π‘π2π‘
+ 4π΄2 π‘2
π2π‘
+ 2π΄1 π2π‘
+ 4π΄1 π‘π2π‘
+
4π΄0 π2π‘
π¦β²β²β²
π
= 12π΄2 π2π‘
+ 12π΄1 π2π‘
+ 8π΄0 π2π‘
+ 24π΄2 π‘π2π‘
+ 8π΄1 π‘π2π‘
+ 8π΄2 π‘2
π2π‘
π¦β²β²β²
β 5π¦β²β²
+ 25π¦β² β 125π¦ = (β500π‘2
+ 465π‘ β 387)π2π‘
12π΄2 π2π‘
+ 12π΄1 π2π‘
+ 8π΄0 π2π‘
+ 24π΄2 π‘π2π‘
+ 8π΄1 π‘π2π‘
+ 8π΄2 π‘2
π2π‘
β 5{2π΄2 π2π‘
+
8π΄2 π‘π2π‘
+ 2π΄1 π2π‘
+ 4π΄2 π‘π2π‘
+ 4π΄2 π‘2
π2π‘
+ 2π΄1 π2π‘
+ 4π΄1 π‘π2π‘
+ 4π΄0 π2π‘ } +
25{2π΄2 π‘π2π‘
+ π΄1 π2π‘
+ 2π΄2 π‘2
π2π‘
+ 2π΄1 π‘π2π‘
+ 2π΄0 π2π‘} β 125{(π΄2 π‘2
+ π΄1 π‘ +
π΄0)π2π‘} = (β500π‘2
+ 465π‘ β 387)π2π‘
(2π΄2 + 17π΄1 β 87π΄0)π2π‘
+ (34π΄2 β 87π΄1)π‘π2π‘
+ (β87π΄2)π‘2
π2π‘
= β500π‘2
π2π‘
+
465π‘π2π‘
β 387π2π‘
ο· β87π΄2 = β500
π΄2 =
500
87
ο· 34π΄2 β 87π΄1 = 465
34 (
500
87
) β 87π΄1 = 465
π΄1 =
β23455
7569
ο· 2π΄2 + 17π΄1 β 87π΄0 = β387
2 (
500
87
) + 17 (
β23455
7569
) β 87π΄0 = β387
π΄0 =
2617468
658503
23. π¦π = (
500
87
π‘2
β
23455
7569
π‘ +
2617468
658503
) π2π‘
π¦ = π¦π + π¦π
π¦(π‘) = π1 π5π‘
+ π2 cos 5π‘ + π3 sin 5π‘ + (
500
87
π‘2
β
23455
7569
π‘ +
2617468
658503
) π2π‘
π¦β²
(π‘) = 5π1 π5π‘
β 5π2 sin 5π‘ + 5π3 cos 5π‘ + (
1000
87
π‘ β
23455
7569
) π2π‘
+ (
500
87
π‘2
β
23455
7569
π‘ +
2617468
658503
) (2π2π‘)
π¦β²β²(π‘) = 25π1 π5π‘
β 25π2 cos5π‘ β 25π3 sin5π‘ +
1000
87
π2π‘
+ (
1000
87
π‘ β
23455
7569
) (2π2π‘) +
(
1000
87
π‘ β
23455
7569
) (2π2π‘) + (
500
87
π‘2
β
23455
7569
π‘ +
2617468
658503
) (4π2π‘)
π¦(0) = 0
0 = π1 + π2 +
2617468
658503
π1 + π2 = β
2617468
658503
................................... (1)
π¦β²(0) = 0
0 = 5π1 + 5π3 β
23455
7569
+
5234936
658503
5π1 + 5π3 = β
3194351
658503
π1 + π3 = β
3194351
3292515
.................................... (2)
π¦β²β²(0) = 0
0 = 25π1 β 25π2 +
1000
87
β
46910
7569
β
46910
7569
+
10469872
658503
25π1 β 25π2 = β
9876532
658503
.................................... (3)
25π1 + 25π2 = β
65436700
658503
................................... (1)
50π1 = β
75313232
658503
π1 = β
75313232
32925150
+
24. From equation (1), we get the value of c2.
π2 = β
2617468
658503
+
75313232
32925150
π2 = β
55560168
32925150
From equation (2), we get the value of c3.
π3 = β
3194351
3292515
+
75313232
32925150
π3 =
43369722
32925150
π¦(π‘) = β
75313232
32925150
π5π‘
β
55560168
32925150
cos 5π‘ +
43369722
32925150
sin 5π‘ + (
500
87
π‘2
β
23455
7569
π‘ +
2617468
658503
) π2π‘