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a question I answered,

Solving the nonlinear Diophantine equation $x^2-3x=2y^2$

has apparently not helped the student enough. I answered his email today, maybe that will help. In particular, I wrote out the Cayley-Hamilton thing with no matrices.

Meanwhile, this exact diophantine equation has been asked about before on Main. I am unable to locate such, partly because there is such variety in the way people ask about these things, many disguises.

So that is the question, what are a few previous instances of, essentially, this diophantine equation on Main?

EDIT: I did try google with

x^2 - 3 x = 2 y^2 site:math.stackexchange

No joy

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    $\begingroup$ Not currently helpful, but I think it'd be cool if bits of Latex had invisible, searchable (possibly by google) hashes associated with them so that typing something in a sufficiently canonical form would find it. It wouldn't help if someone remembered it only as, say, $x^2-3x-2y^2=0$ and didn't think to try anything else, but maybe the process could be permutation-invariant (so that $x+y$ turns up $y+x$ since they have the same amount of each character) or match small tokens as well, and strip idiosyncratic stuff like whitespace. This is probably a silly idea and ought to be scrapped though. $\endgroup$ – Vandermonde Oct 29 '15 at 3:04
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    $\begingroup$ Here's something similar though not exactly the same: How can I find the integer solutions to $x^2 + x - 2y^2 = 0$? $\endgroup$ – hardmath Nov 1 '15 at 11:40
  • $\begingroup$ @hardmath, thanks. I had some specific memory, maybe that other question was deleted. Anyway, the youngster did email me, I sent him two pages Latex, probably the best that can be done. $\endgroup$ – Will Jagy Nov 1 '15 at 17:38

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