Hi

I'm somewhat embarassed to be asking such a simple question but hopefully someone would be kind enough to help me out.

I've been asked to find the first and second derivatives ofA = ln xso I got the following, which agreed with the answers given:

A' = 1/x

However, my confusion is with the second derivative. I prefer to usex^-1rather than1/x. Usingx^-1would give me-1*x^-1-1:

A'' = -x^-2or-1/x^2

The answer given is1/x^2(ie positive, rather than the negative answer I get).

Would somebody be kind enough to tell me which is correct and, if I'm wrong, please explain where I've gone wrong. Thanks very much.

Dave.