to find the inverse of a function you need to isolate the x
[tex]y = - \frac{x}{10} + \frac{1}{2} \\ y - \frac{1}{2} = \frac{ - x}{10} \\ 10y - 5 = - x \\ - 10y + 5 = x[/tex]
after you are done replace every x with y and every y with x (it's optional, i personaly don't do it but you need to do it if your teacher tells you so):
-10x+5=y
