for question 3.

f(x)=2x sinx cosx

I am getting

f'(x)= 2x(-sin^2(x)+ cos^2(x))+ (2sin(x)* 2cos(x))

any advice on how to correctly answer the problem?

for question 3.

f(x)=2x sinx cosx

I am getting

f'(x)= 2x(-sin^2(x)+ cos^2(x))+ (2sin(x)* 2cos(x))

any advice on how to correctly answer the problem?

Well, I’m not sure why you’ve got 2\sin(x) *and* 2\cos(x) in your last term. I suspect you’ve done something like:

2(\sin(x) \cos(x)) = 2\sin(x) 2\cos(x)

But that’s not correct.