Finding the inverse

Question

If f(x)=ln(9x+b), find f^−1(x) in terms of b.

Answer 1

y=ln(9x+b)  -->   e^y=9x+b  -->   9x=e^y-b  -->  x=(1/9)(e^y-b)

so f^-1(y)=(e^y-b)/9  from here  f^-1(x)  is easy to find.