Question 592124
I'll expand everything in order to avoid using the product rule.


*[tex \LARGE f(x) = x^{\frac{7}{3}} - 9x^{\frac{1}{3}}]


*[tex \LARGE f'(x) = \frac{7}{3}x^{\frac{4}{3}} - 9(\frac{1}{3})x^{-\frac{2}{3}} =   \frac{7}{3}x^{\frac{4}{3}} - 3x^{-\frac{2}{3}}]


Set to zero and find all possible values of x (remember to check them). Also, check the endpoints x = -4 and x = 2, as the min/max could occur there.