1, the unknown is the value to be determined when solving the equation, and it is also used as a metaphor for things that are not known yet. In mathematics, we often use symbols X or Y to mark unknowns, and we can use them in equality or inequality relations to help us solve problems.
2. Any letter can represent an unknown number, and the most commonly used ones are X, Y, Z, A, B, C ... An equation containing an unknown number like this is called a mathematical equation. Graphics can also represent unknowns.
3. In Arabic, SHeenlan stands for something, while al-SHeenlan stands for something unknown. But at that time, most Spaniards couldn't pronounce SH, so they used the "on" sound of CK in ancient Greece. It is similar to Latin X in writing and gradually becomes X in common use.
4. In ancient China, unknowns were not represented by symbols, but equations were solved by calculation. In the Song and Yuan Dynasties, Li Zhi used "Li Tianyuan" to express the unknown, and wrote a yuan word as a symbol beside the corresponding coefficient. In the Yuan Dynasty, Zhu Shijie (about13rd century) expressed four unknowns in terms of heaven, earth, people and things, and established the theory of four-dimensional higher-order equations.
5. Unknown numbers are involved from the beginning when they come into contact with mathematical problems, and all kinds of unknown numbers appear in mathematics, physics, chemistry and biology.