Unipotent and Unit-Regular Elements in Certain Subrings of M_2 (Z)

Abstract

We presented a simple and direct way to construct a unipotent unit and clean but not nil-clean element in a ring. New examples of unipotent/unit-regular elements that are not nil-clean are given. We also study the product of two idempotents/unit-regulars which are unit-regular. The studies are exemplified in two subrings of M_2 (Z).