Consider the cubic function f(x) = ax + bx-+ ex + d. a. Show that f can have 0, 1, or 2 critical points. Give examples and graphs to support your argument. b. How many local extreme values can f have? . . . a. How can the critical point(s) of f(x) be found using the derivative, f (x)? Select the correct choice and, if necessary, fill in the answer box to complete your choice. A. Critical points occur when f' (x) = 0 . O B. Critical points occur when f(x) is undefined. O C. Critical points occur when f'(x) is undefined. O D. Critical points occur when f(x) = Find the derivative of the given function. f' (x) =