Let $f(x) = \displaystyle \frac{1}{ax+b}$ where $a$ and $b$ are nonzero constants. Find all solutions to $f^{-1}(x) = 0$. Express your answer in terms of $a$ and/or $b$.
y = ax + b
y - b = ax
[ y - b] / a = x swap x and y and for y write f-1 (x)
So
f-1 (x) = [ x - b ] / a = 0 when b = x
+618 
