Find f(x) and g(x) so that the function can be described as y = f(g(x)).

y = 4/x^2+9

I'm assuming all of (x^2+9) is in the denominator. If that assumption is correct, then,

One possible answer is

Another possible answer is

There are many ways to do this. The idea is that when we have f( g(x) ), we basically replace every x in f(x) with g(x)

So in the first example above, we would have

In that third step, g(x) was replaced with x^2+9 since g(x) = x^2+9.

Similar steps will happen with the second example as well (when g(x) = x^2)