A Function Is Given $U ( x ) = 4 \left( x ^ { 3 } - x \right)$

Essay

A function is given.
(a) Find all the local maximum and minimum values of the function and the value of x at which each occurs.
(b) Find the intervals on which the function is increasing and on which the function is decreasing. State all answers correct to two decimal places.
$U ( x ) = 4 \left( x ^ { 3 } - x \right)$