X marks the unknown in algebra – but X's origins are a math mystery
- Written by Peter Schumer, Professor of Mathematics and Natural Philosophy, Middlebury
The use of the letter x as a mathematical unknown is a relatively modern convention. Algebra has been around for a lot longer.Daryl Benson/Stockbyte via Getty ImagesEven though x is one of the least-used letters in the English alphabet, it appears throughout American culture – from Stan Lee’s X-Men superheroes to “The...





