Fermat's factorization method: Difference between revisions

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actually there's more errors here, just restoring old correct version for now
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Each odd number has such a representation. Indeed, if <math>N=cd</math> is a factorization of ''N'', then
:<math>N = \left(\frac{c+d}{2}\right)^2 - \left(\frac{c-d}{2}\right)^2.</math>
 
Since ''N'' is odd, then ''c'' and ''d'' are also odd, so those halves are integers. (A multiple of four is also a difference of squares: let ''c'' and ''d'' be even.)