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Prove the following statements by contradiction a) If x∈Z is divisible by both even and odd...

Prove the following statements by contradiction

a) If x∈Z is divisible by both even and odd integer, then x is even.

b) If A and B are disjoint sets, then A∪B = AΔB.

c) Let R be a relation on a set A. If R = R−1, then R is symmetric.

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