Math Help - composite and invers function problem

1. composite and invers function problem

need help with inverse function problem.

1.find the inverse for:
$f(x)=x^4+2 x^3+ 3 x^2 + 2 x^2+1$?

and

this one is composite function problem
2.if $f(x y)=f(x+y)$ and given that $f(7)$=7, find the value of f(49)?

2. 1.
i've try to simplify the function:
so,
$f(x)= (x^\frac{1}{2})^8 +2(x^\frac{1}{2})^6 + 3(x^\frac{1}{2})^4 + 2(x^\frac{1}{2})^2 +1$
and ????