Logarithms

f(x) = log₃ (x + 1)      let's write "y" for f(x)   .....and we have...

y = log₃ (x + 1)

This says that......in exponential form....

3^y  = x + 1       subtract 1 from both sides   

3^y - 1   = x          exchange x and y

3^x - 1  = y         and for y, write  f^-1(x)

So

f^-1(x)  = 3^x - 1        ....and......

f^-1(2)  = 3*2  - 1   = 8

So....the point  (2, 8) is on the inverse

Check to see that the point (8, 2)  is on the original graph....and it is  !!!!