1. The problem statement, all variables and given/known data I'm having a hard time differentiating when to use log instead of ln, vice versa. Are there any general rules to follow? For example I have to evaluate 4u^-3 + u^-1. 2. Relevant equations f'(1/u) = log u f'(1/u) = ln u 3. The attempt at a solution I put -2u^-2 + log(u) but the textbook solution shows the same answer except with ln.