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: A simple solution by SilverKnight)

You say "Commutative means that (a#b)#c = a#(b#c)." That is the associative property. The commutative property is that a#b = b#a.

Posted by Charlie on 2003-10-19 13:25:13