Answer
Relative maximum at $x=-4$
Relative minimum at $x=-2$
Work Step by Step
In the interval $(-\infty,-4)$, $f(x)$ is increasing implying that $f'(x)>0$.
In the interval $(-4,-2)$, $f(x)$ is decreasing implying that $f'(x)<0$.
As the sign of the derivative changes from $+$ to $-$, the point $x=-4$ is a relative maximum.
Similarly, about the point $x=-2$, $f'(x)$ changes sign from $-$ to $+$. Therefore, $x=-2$ is a point of relative minimum.
The given function is increasing in the intervals $(-\infty,-4)\cup(-2,\infty)$ and decreasing in $(-4,-2)$. At the relative extrema points, $f'(x)=0.$
