solve and explain

(a) Let R be a relation on the set of ordered pairs of positive integers such that (a,b)R(c,d) if and only if ad=bc. Show that R is an equivalence relation. (b) Let R be a relation on the set of ordered pairs of non-negative integers such that (a,b)R(c,d) if and only if ad=bc. Is R an equivalence relation? Which of the properties of reflexivity, symmetry and transitivity does it satisfy? Explain