Question

How do you find critical points on a graph?

Answer 1

Critical points for a function `f` are numbers (points) in the domain of a function where the derivative `f'` is either `0` or it fails to exist.

So look for places where the tangent line is horizontal (`f'(c)=0`)

Or where the tangent line does not exist (cusps and discontinuities -- jump or removable) and the tangent line is vertical.