Question - integrate the following:

(int) (4- (e^x))^3 e^x dx

attempt:

u = (4 + e^x)

n = 3

du = e^x

therefore answer is:

((4 + (e^x))^4) / 4 + c

which is incorrect, and should be:

4 / (e^(x^1/2)) + c

Stared at it for a while and can't figure it out. Any help, thanks?