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When did mathematicians begin to use the letter x to denote unknown values ? Gérard Lang

Gérard Lang
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    Have a look at this https://www.ted.com/talks/terry_moore_why_is_x_the_unknown?language=en – Amir Asghari Oct 14 '15 at 08:54
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    ...or don't. Florian Cajori's book "A history of mathematical notations" goes to great detail to explain how such popular theories came to be and how they are essentially not supported by any evidence. As far as the earliest documented use, it goes back to Descartes, who simultaneously introduced y and z (and a,b,c) to denote unknowns. (pages 380-383 in Cajori's book) – Gjergji Zaimi Oct 14 '15 at 09:06
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    http://mathoverflow.net/questions/104031/why-unknowns-are-usually-denoted-by-x?rq=1 – Carlo Beenakker Oct 14 '15 at 09:08
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    http://mathoverflow.net/q/30307/461 – Pierre-Yves Gaillard Oct 14 '15 at 09:49

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