[SOLVED] inverse of a function

I'm trying to take the inverse of the function

I think I've got it following this procedure

[tex]y = \frac{-3-4x}{x-2}[tex]

I worked that a few times and am pretty confident in my answer. The proof is in plugging that back into the original equation and seeing if I get x, and this is where I'm fumbling about

which, unless I'm blind, does not equal x. I hope the above isn't too confusing.

Assuming my initial answer is correct, what am I doing wrong when I'm trying to verify it?