Give a carefully worded proof for the following statements using either direct or contrapositive proof. 1) 2) If a is an integer, then 2 | (a² +3a+ 4). If two integers have opposite parity, then their...

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Extracted text: Give a carefully worded proof for the following statements using either direct or contrapositive proof. 1) 2) If a is an integer, then 2 | (a² +3a+ 4). If two integers have opposite parity, then their sum is odd.