Consider a binary operation # that is closed under the set of integers (if a and b are integers, then a#b is an integer).

Assume that, for all integers a and b, it is true that (a#b)#a=b.

Prove that a#(b#a)=b.

(In reply to re(4): A simple solution by SilverKnight)

The problem does not say to assume that if F(G(x))=x, then G(F(x)) must also equal x. It's true, of course .. because that's what the problem is asking you to prove.

Posted by DJ on 2003-10-20 02:18:01