Let y = y(x) be the solution of the differential equation x dydx - 2y = 2 + 3 x, x (- 2, 2 ), y(0) = - 74. Then y ( 6 ) is equal to :
- - 52
- -3 2 - 7
- - 54
- -3 3 - 7
Answer
(1) - 52
Solution
dydx - (2 x)y = (2 + 3 x) x (linear)
I.F. = e- 2 x dx = e-2 x
y e-2 x = (2 + 3 x) x e-2 x dx
Put x = t: (2 + 3t)e-2t dt = -e-2t - 3t2e-2t - 34e-2t + C
y e-2 x = -e-2 x ( 74 + 32 x ) + C
y = - 74 - 32 x + Ce2 x
y(0) = - 74 ⇒ C = 0
y ( 6 ) = - 74 - 34 = - 52
Answer: (1)