Find the inverse of the following function.

Let f(x) be y.

y  = x³ + 3

Switch x and y:

x = y³ + 3

Now you need to isolate y and you would get inverse function.

x - 3 = y³

∛(x-3) = y

Final  f ⁻¹(x) = ∛(x-3)

Hope this helps.