1. ## Critical Numbers

How can I find the critical numbers and the open intervals on which the function is increasing or decreasing ?

$y=x^\frac{2}{3} - 4$

If you could show me the techniques for solving this problem step by step that'd be great.

2. Find y'.

For which values of x is y' = 0 ?
For which values of x is y' undefined ?
Test some x values slightly above or below each of the above x values.