X marks the unknown in algebra – but X's origins are a math mystery
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 X-Files” TV series. The letter x often symbolizes something unknown, with an air of mystery that can be appealing – just look at Elon Musk with SpaceX, Tesla’s Model X, and now X
Source: yahoo.com