What is an indirect proof for the theorem: If n^2+1 is odd, then n is even?

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Darkrise666
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Here's the problem.

Theorem: If n^2+1 is odd, then n is even. Give indirect proof.
 
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Discussion

What have you thought to do? I would suggest thinking about the properties of even/odd numbers.

Also, I believe this is in the wrong section. It should be in math, not physics.
 

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