Answer
$f[g(x)]=\displaystyle \frac{2}{(2-x)^{4}}$
$g[f(x)]=2-\displaystyle \frac{2}{x^{4}}$
Work Step by Step
In the expression for f(x), replace x with g(x)
$f[g(x)]=\displaystyle \frac{2}{(g(x))^{4}}$
$=\displaystyle \frac{2}{(2-x)^{4}}$
In the expression for g(x), replace x with f(x)
$g[f(x)]=2-[f(x)]$
$=2-[\displaystyle \frac{2}{x^{4}}]$
$=2-\displaystyle \frac{2}{x^{4}}$