I'm trying to isolate y so I wrote: "solve for y, (1+t)^y = x(((1 + g)^(y+1) - 1)/ g)"
Y is in the exponents on both sides of the equation. It's really tough to isolate by hand but I thought Wolfram would isolate y easily. What did I do wrong?
It's a transcendental (as opposed to algebraic, e.g. polynomial) equation in y, and Mathematica simply does not know of a way to solve it for y.
Solve[(1 + t)^y == x*((1 + g)^(y + 1) - 1)/g, y]
During evaluation of In:= Solve::nsmet: This system cannot be solved with the methods available to Solve. >>
Out= Solve[(1 + t)^y == ((-1 + (1 + g)^(1 + y)) x)/g, y]
Wasn't for lack of trying...
What this means, among other things, is that you didn't do anything wrong, other than perhaps having expectations too high for what could be done here.