I can't do any of these problems really. Going through them all I felt really good, I thought they were easy and that I had finally got a grasp on this stuff. I think went to check the answers and I didn't get a single one correct. Anyways I will just pick out a random one, I can't get any of these on my own.
I am sure this one is pretty easy for most people.
differentiate $\sin x \ln(5x)$ I get $\cos x(\ln5x)+\sin x/5x$ which is an incorrect answer. Not sure why.