1. Let S be the set of all nonzero real numbers. That is, S = R - {0}. Consider the relation R on S given by xRy iff xy > 0.
(a) Prove that R is an equivalence relation on S, and describe the distinct equivalence classes of R.
(b) Why is the relation R_{2} on S given by xR_{2}y iff xy < 0 NOT an equivalence relation?