MathDB
Putnam 2001 A1

Source:

February 26, 2012
Putnamcollege contests

Problem Statement

Consider a set SS and a binary operation ∗*, i.e. for each a,b∈Sa,b\in S, a∗b∈Sa*b\in S. Assume (a∗b)∗a=b(a*b)*a=b for all a,b∈Sa,b\in S. Prove that a∗(b∗a)=ba*(b*a)=b for all a,b∈Sa,b \in S.
Back to ProblemsView on AoPS