Abstract

In this paper we prove that if R is a ring with 1 as an identity element in which xmxnZ(R) for all xR and fixed relatively prime positive integers m and n, one of which is even, then R is commutative. Also we prove that if R is a 2-torsion free ring with 1 in which (x2k)n+1(x2k)nZ(R) for all xR and fixed positive integer n and non-negative integer k, then R is commutative.