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Let Z be the set of all integers and R be the relation on Z defined as R = {(a, b): a, b ∈ Z) and (a – b) is divisible by 5. Prove that R is an equivalence relation. |
Answer» Reflexive: Since 5 divides a – a for all a ∈ Z, therefore, R is reflexive. Symmetric: (a, b) ∈ R ⇒ 5 divides a – b ⇒ 5 divides b – a ⇒ b – a ∈ R ∴ R is symmetric. Transitive: (a, b) ∈ R and (b, c) ∈ R ⇒ a – b and b – c are both divisible by 5 ⇒ a – b + b – c is divisible by 5 ⇒ (a – c) is divisible by 5 ⇒ (a, c) ∈ R ∴ R is transitive. Since R is reflexive, symmetric and transitive, therefore, R is an equivalence relation. |
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