The function is increasing for:
[tex](-\infty,-4)\cup(4,\infty)[/tex]
And the function is decreasing for:
[tex](-4,4)[/tex]
The local maximum (or minimum) occurs when there may be higher (or lower) points elsewhere but not nearby.
Therefore, the local maximum of the function is:
[tex](-4,128)[/tex]
And the local minimum of the function is:
[tex](4,-128)[/tex]
