Think of a function as an equation from which X can be solved.

Get x = 2 y

Then change x into y, and change y into x to get the inverse function expression.

Y = 2 x

The domain of the inverse function is the domain of the original function.

y=log3 (x+6)

x+6=3^y

x=3^y -6

Inverse function y = 3 x-6

The range of the original function is r, so the domain of the inverse function is R.

So f- 1 (x) = 3 x-6 (x ∈ r)