Determine the intervals of increasing/decreasing and the critical points of the function using the graph of $f^{\prime }\left(x\right)$.

Critical points: $x=\{-2,-1,1\}$

Increasing on $(1,\infty )$

Decreasing on $(-\infty ,-1)$

Critical points: $x=\{-2,1\}$

Increasing on $(-\infty ,-2)$

Decreasing on $(1,\infty )$

Critical points: $x=\{-2,-1,1\}$

Increasing on $(-1,1)$ $\cup$ $\left(1,\infty)\right.$

Decreasing on $\left(-\infty,-2\right)$ $\cup$ $(-2,-1)$

Critical points: $x=\{-2,-1,1\}$

Increasing on $(-2,-1)$ $\cup$ $(1,\infty )$

Decreasing on $(-\infty ,-2)$ $\cup$ $(-1,1)$