Dollar Shave Club!: http://dollarshaveclub.com/brainfood If you happen to like our videos and have a few bucks →→Subscribe for new videos every day! https://www.youtube.com/user/TodayIFoundOut?sub_confirmation=1 Never run out of things to say at the water cooler with TodayIFoundOut! Brand new videos 7 days a week! In this video: Algebra was born in the Middle East, during the Golden Age of medieval Islamic civilization (750 to 1258 AD), and its early form can be seen in the work of Muhammad Al-Khwarizmi and his 9th century book, Kitab al-jabr wal-muqabala (al-jabr later morphing into algebra in English). During this heyday, Muslim rule and culture had expanded onto the Iberian Peninsula, where the Moors encouraged scholarship in the sciences and math. Want the text version?: http://www.todayifoundout.com/index.php/2014/11/origins-mathematical-convention-using-x-unknown/ Sources: http://www.storyofmathematics.com/islamic_alkhwarizmi.html http://www.corestandards.org/standards-in-your-state/ http://www.theatlantic.com/education/archive/2014/04/confusing-math-homework-don-t-blame-the-common-core/360064/ http://www.storyofmathematics.com/17th_descartes.html http://www.oecd.org/pisa/keyfindings/pisa-2012-results.htm http://en.wikipedia.org/wiki/Moors http://www.seanmathmodelguy.com/?p=655 http://www.ted.com/talks/terry_moore_why_is_x_the_unknown/transcript?language=en http://www.newton.dep.anl.gov/askasci/math99/math99228.htm http://www.livescience.com/15004-represents-unknown-quantity-variable.html http://io9.com/why-do-we-use-the-letter-x-to-represent-the-unknown-1588933259 http://en.wikipedia.org/wiki/X http://mathoverflow.net/questions/30307/explanation-why-x-y-z-are-always-variables/30414#30414 http://jeff560.tripod.com/variables.html http://www.encyclopediaofmath.org/index.php/Mathematical_symbols http://en.wikipedia.org/wiki/Ren%C3%A9_Descartes http://en.wikipedia.org/wiki/Cogito_ergo_sum https://ed.stanford.edu/news/poor-ra