How do i justify if these functions are inverses of each other f(x)=x^3 +4 & g(x)=3(radical sign) -4

You plug them into each other for x like so:
(3(radical sign)-4)^3+4
-4+4
You're left with x
Then do the same for the other one
3(radical sign)(x^3+4)-4
X+4-4
Left with x again there fore it is an inverse

A) 144.44 sq inches i believe