Generally speaking, in mathematics, X is used to represent unknowns, which can directly participate in operations and is widely used in life. Like other letters such as y and z, it can represent all numbers. For example, y=a(x-h) in the equation? +k(a≠0, a, h and k are constants), and x is an unknown term or quantity.

2. Multiply by symbols

163 1 year, the British mathematician William Oughtred expressed two numbers multiplied by "X" for the first time in his book Clavis Mathematicae, which became more and more popular.

In the letter 1698 to johann bernoulli on July 29th, Leibniz proposed to use the dot "x" to represent multiplication, in case "x" is confused with the letter "x".

Case first left and then right. As shown in the figure below:

X: The 24th letter of the English alphabet. Pronunciation /eks/ is the letter with the fewest initials in English letters. x？ It means unknown and infinite, and X also has "goal" and "hope". Some words are obscure and difficult to translate directly, but they are represented by "XXX", and so on.