

2+2=4, Why? - ssapkota
http://www.mathmojo.com/interestinglessons/why%20do2plus2equal4/why%20do2plus2equal4.html

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infinity
From the title and the original question in the article I expected something
like a proof in a system of formal arithmetic, maybe a discussion of the Peano
axioms or a discussion of different possible representations of the natural
numbers using sets (like von Neumann ordinal numbers) and the really
interesting question if numbers are sets.

<http://en.wikipedia.org/wiki/Peano_axioms>

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egiva
Well, the post wasn't very well written probably, but you can argue that they
are talking about two concepts: Axioms and Notation. If you used base 2, or
base 3 (or base -2, -3) math, then that particular notation would work out
differently than, say, base 8 math, etc. For Axioms, here you go:
<http://en.wikipedia.org/wiki/Axiom>

