函數:f(x)=X^2/3(5-X) 求: A.此函數的臨界值 B.此函數遞增及遞減之區域 C.用一階極值判定法求出此函數得相對極值?

a. I don't know sorry
b. Just solve f'(x)=0 and you can graph the graph roughly
c. same, just solve f'(x)=0 and substitute the x into f(x) and the find the value