The inverse function occurs when the original function, f(x), is translated about the y = x line, so to find the inverse function, we swap the x and y values and then solve for y.
[tex]y = 9x + 2 \Rightarrow x = 9y + 2[/tex]
[tex]9y = x - 2 \text{ so } f^{-1}(x) = \frac{1}{9}(x - 2)[/tex]