Exercise 1.2.8 (Same parity)

Two integers are said to be of same parity if they are both even or both odd; if one is even and the other odd, they are said to be of opposite parity, or of different parity. Given any two integers, prove that their sum and their difference are of the same parity.

Answers

Proof. If m and n are integers, ( m + n ) ( m n ) = 2 n is even, therefore m + n and m n are of same parity.

(If m n is odd, then m + n = ( m n ) + 2 n is odd, and if m n is even, then m + n = ( m n ) + 2 n is even.) □

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2024-06-16 11:20
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