# Thread: im having trouble with this one.

1. ## im having trouble with this one.

i cant seem to figure this out

It is easy to check that for any value of c, the function y=ce^-2+e^-x
is solution of equation y'+2y=e^-x
Find the value of c for which the solution satisfies the initial condition y(-4)=10
c=?

thanks for any help

2. Hello,

y=ce^-2+e^-x

I guess it's -2x

So $y(x)=c*e^{-2x}+e^{-x}$

$y(-4)=10 \leftarrow 10=c*e^8+e^4$

$c*e^8=10-e^4$

$c=\frac{10-e^4}{e^8}$

This is really awful !

3. that worked your on fire! thanks a lot.