Let y = y(x) be the solution of the differential equation dydx + 3( 2 x)y + 3y = 2 x, y(0) = 13 + e3. Then y ( 4 ) is equal to :
- 43
- 23 + e3
- 43 + e3
- 23
Answer
(1) 43
Solution
dydx + 3( 2 x + 1)y = 2 x
dydx + (3 2 x)y = 2 x (linear)
I.F. = e 3 2 x dx = e3 x
y e3 x = 2 x e3 x dx = 13e3 x + c
y = 13 + c e-3 x
y(0) = 13 + c = 13 + e3 c = e3
y ( 4 ) = 13 + e3 e-3
= 13 + 1 = 43
Answer: (1)