Answer
$a.\qquad $see image below
$b.\quad (-\infty,\infty)$
$c.\quad $Decreases on$ ( -\infty,-2.83)\cup(0,2.83)$
Increases on $( -2.83,0)\cup(2.83,\infty)$
Work Step by Step
$a.$
(graphed with online graphic calculator at desmos.com)
$b.$
$f$ is defined for all reals, $(-\infty,\infty)$
$c.$
f has a local maximum at$ x=0$
and a minima at $x\approx\pm 2.83.$
Decreases on$ ( -\infty,-2.83)\cup(0,2.83)$
Increases on $( -2.83,0)\cup(2.83,\infty)$