Answer
a) $fog=gof=x$
b) Bissector of first and third quadrants
Work Step by Step
a) In order to g be the inverse of f, we need to have:
$f(g(x))=x$
$g(f(x))=x$
We mean that the composite function fog and gof has to be the identity function $h(x)=x$
b) The graphs of f and g are simmetric with respect to the bissector of first and third quadrant. This occurs because $f=g^{-1}$
