Writing to Learn Let $f(x)=(x-2)^{2 / 3}$
(a) Does $f^{\prime}(2)$ exist?
(b) Show that the only local extreme value of $f$ occurs at $x=2$ .
(c) Does the result in (b) contradict the Extreme Value Theorem?
(d) Repeat parts (a) and (b) for $f(x)=(x-a)^{2 / 3}$ , replacing 2 by $a$ .