[SOLVED] ring theory problem 1. The problem statement, all variables and given/known data True or false. The product of two nonunits in Z_n may be a unit. 2. Relevant equations 3. The attempt at a solution If a and b are two non units in Z_n, and ab <= n, then the result is clear, since ab would not be relatively prime to n. But what about if ab > n ? Obviously the units form a group under multiplication, but I don't see how that helps.