Q.

If x = x(t) is the solution of the differential equation (t+1)dx=(2x+(t+1)4)dt, x(0) = 2, then x(1) equals __________.           [2024]


Ans.

(14)

We have, (t+1)dx=(2x+(t+1)4)dt

⇒ dxdt=2xt+1+(t+1)3; P=–2t+1, Q=(t+1)3

So, I.F. =e∫Pdt=e∫–2t+1dt=e–2 log (t+1)=(t+1)–2

The Solution of given differential equation is given by x(I.F.)=∫Q·(I.F.)dt+C

⇒ x(t+1)2=∫(t+1)3(t+1)2dt+C

⇒ x(t+1)2=∫(t+1)dt+C ⇒ x=(t+1)2[t22+t+C]

Putting x(0) = 2, we get

2=(1)2(0+0+C) ⇒ C=2

∴   x=(t+1)2(t22+t+2)

At t=1, x = (2)2(12+1+2)=4(72)=14.