Talk:Proof by contrapositive/Archive 1

References?
This article is flagged stating it lacks references, but I see two references listed. Admittedly, these are web references, but they are references nonetheless. I don't see think this note should be here (maybe a different note, asking for better references). I moved the existing references to in-line citations, added one reference (to the definition of contrapositive), and removed the flag. Geoffrey.landis (talk) 15:57, 4 December 2010 (UTC)

This article is extremely useful; I feel like instead of deleting it, references should be added. There are plenty of references out there. — Preceding unsigned comment added by 192.154.63.76 (talk) 20:06, 1 October 2012 (UTC)

Self-contradicting
This statement: "A direct proof is difficult, so a proof by contrapositive is preferable."

Is contradicted a little later... "Despite what is said above, a direct proof is much simpler."

Suggest: change first statement to: "Here is a proof by contrapositive." Bdbluesman (talk) 16:50, 21 February 2013 (UTC)

The proof using properties of prime numbers and multiplicites in prime factorizations is definitely much harder than the proof by contrapositive provided. — Preceding unsigned comment added by 141.216.13.56 (talk) 15:17, 12 March 2013 (UTC)