I see what I did now I never did 1 - 16/64. Because I left in x I didn't subsitute the -4 in for x.

But if you don't mind I have another question I'm trying to do

I want to find f'(x) again and I was trying to follow steps in my book. I got sin(5 cos 7x)+(5 cos 7x)(cos x) but the programs says thats wrong. So I tried a differenet problem similiar to it

If

and got 6e^(x*cos(x))(-sin(x)) but it says thats wrong. I'm following the rules right out of the book and the trig functions but not sure. Are you able to see what i'm doing wrong here? Thanks