- #1

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I didn't get very far, but here's my attempt at it...

Let A be a set that contains 1 and contains n whenever it contains n+1. Now, let there be a non empty set B that contains all natural numbers not in A. By the well-ordering theorem, B must contain a least element m. m≠1...

Aside from hints to head me in the right direction, any tips on how to improve at proofs or just the way to go about thinking about questions to prove would be helpful.