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 My solution by Ashlee)

Your solution assumes the commutative property is true. You cannot assume that from what the problem tells you.

Posted by Brian Smith on 2003-10-21 11:05:20