The fact that you spent that time solving nothing. You can manipulate any equation by setting x= whatever, but that doesn't mean that it's useful, especially when trying to prove something like this. You're manipulating an equation that's getting you nowhere, that's the problem.
Also, once you have found x = to something, it is equal to that number, and cannot be changed for that set of equations. So x=1, but later on you find x+1=1. This is one of many points where you need to realize you fucked up the problem. x cannot equal 1 and 2 at the same time.
And pertaining to dividing by 0: absolutely not. This is a big no no. This is only useful when taking limits in calculus.
such as
lim x->0 1/x^2 = positive infinity
Read:
http://en.wikipedia.org/wiki/Dividing_by_zeroAlso:
http://en.wikipedia.org/wiki/Invalid_pr … at_2_.3D_1