Question

What is f−1(f(x)) = f(f−1(x)) = equal to????? please help

Answer 1

the assumption here is that the function f(x), has an inverse function of f⁻¹(x), so let's assume that is indeed the case, f⁻¹(x) is the inverse function of f(x).

for functions and their inverse, if they're indeed inverse of each other, then

f⁻¹( f(x) ) = x

f( f⁻¹(x) ) = x.