1. The problem statement, all variables and given/known data There's this one exam problem that I cannot solve... Here it goes: Consider the set Z x Z+. Let R be the relation defined by the following: for (a,b) and (c,d) in ZxZ+, (a,b) R (c,d) if and only if ad = bc, where ab is the product of the two numbers a and b. a) Prove that R is an equivalence relation Z x Z+ b) Show how R partitions Z x Z+ and describe the equivalence classes 2. Relevant equations For equivalence relations we have to proof that it is reflexive (xRx), symmetric (aRb = bRa) and transitive (aRb bRc hence aRc) 3. The attempt at a solution I already did part a... I just have trouble on b... how am I supposed to know the equivalence classes of this?