bureX said:

There's a a^2 - ab ≠ 0 missing somewhere, I think Wink

(by the way, I suck at math)

if a == b, then a^2 == ab and a^2-ab==0. Division by zero is not permitted here Smiley  You can get any answer you want if you divide by zero, just as you can "prove" any proposition if you accept a contradiction, just as any statement about members of the empty set is logically true!