Answer
$a. f(x) = g(h(x))$
$b. f(x) = g(h(x))$
Work Step by Step
$a. f(x)=x^2+1 $
$ say, h(x) = x^2$
$and, g(x)=x+1$
$Therefore, f(x) = g(h(x))$
$b. f(x)=1/(x-3) $
$ say, h(x) = x-3$
$and, g(x)=1/x$
$Therefore, f(x) = g(h(x))$
$$\boxed{\text{Please see additional work shown in attached image.}}$$