Question: 1. Consider a,b ∈ Z and let a ∼ b if a ≡ b (mod 3) or if a ≡ b (mod 5). Is this an equivalence relation? Explain which properties of equivalence relations hold and which don't. If this is an equivalence relation, then list the equivalence classes.
2. Prove that the graph shown in Figure is non-planar.
