Show that the relation Ron Z (Z\{0}) is an equivalence relation: (a,b) R (c,d) if and only if a d = b*c. Thus, for example, (2,5) R (6,15) since 2*15 = 5*6. But, (2,5) !R (4,9) since 2*9# 5*4. (!R means "is not related by R. This is usually written as R with a slash through it, but this editor does not allow this.)