Calculus Help: Mean Value Theorem Let f(x) = x^3 - x on the interval [2,3]. Find all numbers c in the interval (2,3) that satisfy the conclusion of the mean-value theorem. Here's what I did: f '(c) = f(b) - f(a) / (b - a) f '(c) = f(3^3 - 3) - f(2^3 - 2) / (3-2) = 18, but it's incorrect. What am I doing wrong? Please help.