d(x) = *IntegralSign(b^(-x/c) / (f + ax))dx
a, b, c, f are constants
I'm stumped. A little help
The Mathematic site gives the answer in terms of the error function, which can only be approximated. But let's see what your substitution does.
Let
So
(which is pretty much the same form as you started with.)
I can see no way to integrate this (barring some kind of approximation.)
-Dan