1. The problem statement, all variables and given/known data A) If ab+ba = 1 and a^3 = a in a ring, show that a^2 = 1 2. Relevant equations none 3. The attempt at a solution Little confused. If we know that a^3 = a, can't we just multiply each on the right or left side by a^-1 to get a^2 = 1? Or could we only do that if the ring is said to be commutative? edit: I realized that to show that a^2 = 1 in the way I mentioned above that a would have to be a division ring. Normal rings aren't guaranteed to have multiplicative inverses.