1. The problem statement, all variables and given/known data f(x) = 1/ln (10-x) -- I would assume it to be a fairly simple equation, but I am screwing it up 2. Relevant equations What is f'(x)? 3. The attempt at a solution f'(x) = (ln (10-x))^-1 = -(ln (10-x))^-2 * -1 * 1/(10-x) -- 2 negatives cancel out = 1/(10-x) (ln(10-x))2 -- This is as far as I got and I just can tell it isn't correct. Thank you in advance for all help.