S= Set of all integers and R={(a,b),a,b∈S and ab≥0} For reflexive: aRa=a⋅a=a2≥0, so it's reflexive. For symmetric: aRb=ab≥0 and bRa=ba≥0, So relation is symmetric For transitive: For all integers a⋅a≥0. If ab≥0,bc≥0, then also ac≥0 So, Relation Is reflexive, symmetric and transitive. Therefore relation is equivalence.