MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. List the x-values in the graph at which the function is not differentiable. 6) A) X = 2 B) X = 1, X = 2, x = 3 C) X = 1, x = 3 D) Function is differentiable at all points Find the derivative. 7) f(x) = 3x4 + 3x3 + 9