Answer
$\text{a) increasing: }
(3,\infty)
\\\text{b) decreasing: }
(-\infty,-3)
\\\text{c) constant: }
(-3,3]$
Work Step by Step
From the $x-$interval of $
( -\infty, -3)
$ the graph goes down.
From the $x-$interval of $
(-3,3]
$, the graph stays the same.
From the $x-$interval of $
(3,\infty)
$, the graph goes up.
Hence, the graph has the following characteristics at these intervals:
\begin{array}{l}\require{cancel}
\text{a) increasing: }
(3,\infty)
\\\text{b) decreasing: }
(-\infty,-3)
\\\text{c) constant: }
(-3,3]
.\end{array}
