Answer:
When we have a function g(x) such that:
g(x) = y.
Then the inverse, h(x), must be such that:
h(y) = x.
This means that:
g( h(x) ) = x
h( g(x) ) = x.
In this case, g(x) = 41*x^3 + a.
Then:
g( h(x)) = x = 41*h(x)^3 + a.
Now we can solve it for h(x).
x - a = 41*h(x)^3
(x - a)/41 = h(x)^3
∛( (x -a)/41 ) = h(x)
h(x) is the inverse function of g(x).