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Prove either by contradiction or contraposition (using Fundamental Theorem of Arithmetic in either case) that:

$$ ∀k ∈ \mathbb{Z}, [3|(k-2) → 3 |(k^2 - 1)] $$

Any help would be great! Thanks!

m0nhawk
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1 Answers1

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Hint: $k^2 - 1 = (k^2-4) + 3 = (k-2)(k+2) + 3$

DeepSea
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