Answer
See the explanation below.
Work Step by Step
A point on the graph at which the slope of a function $f(x)$ approaches $\infty$ from one side and $-\infty$ from the other side is defined as a cusp on the graph.
For Example:
$f(x)=x^{2/3}$ at $x=0 \\ \implies f'(x)=\dfrac{2}{3x^{1/3}} $
Therefore, we have: $\lim\limits_{x \to 0^{+}}f'(x) =+\infty \\ \lim\limits_{x \to 0^{-}}f'(x) =-\infty$
