People's research on equations can be traced back to ancient times. About 3600 years ago, the mathematical problems written by ancient Egyptians on papyrus involved equations with unknowns. Around 825 AD, Al-Hua Lazimi, a mathematician in Central Asia, wrote a book "Elimination and Reduction", focusing on the solution of equations, which had a great influence on the later development of mathematics.

For a long time, the equation has no special expression form, but is described in general language. /kloc-in the 7th century, the French mathematician Descartes first proposed to use letters such as xy and z to represent unknowns, regarded these letters as ordinary numbers, and connected them with operation symbols and equal signs to form an equation containing unknowns. Later, after continuous simplification and improvement, the equation gradually evolved into the present expression form, such as 6x+8=20, 4x-2y=9, x-4=0 and so on.

China's research on equations also has a long history. China's Ancient Mathematics Works

When the ancient mathematicians in China expressed equations, they only expressed the coefficients of each unknown by calculation, but did not express the unknown by special notation. According to this representation, the equations are arranged in a rectangular digital square, which is very close to the matrix in modern mathematics. Liu Hui, an ancient mathematician in China, pointed out when commenting on the meaning of "equation" that the word "Fang" is closely related to the above-mentioned digital phalanx, while the word "Cheng" means to list equations with unknowns, so the word "equation" in Chinese originated from the method of solving practical problems by listing a group of equations with unknowns. During the Song and Yuan Dynasties, Chinese mathematicians founded "Tianyuan", using "Tianyuan" to represent unknowns and establish equations. The representative work of this method is "Measuring the Circle Sea Mirror" written by mathematician Li Zhi, in which "Setting Tianyuan I" is equivalent to "Setting Unknown X" now.

With the continuous expansion of the research scope of mathematics, the application of equations is more and more extensive, and the function is more and more important, and the types of equations are also developing from simple to complex. However, no matter how the type changes, formal equations are all equations with unknowns, and they all express the equivalent relationship involving unknowns; The basic idea of solving the equation is to gradually change the unknown number into the form represented by the known number according to the equivalence relation, which is the essence of the equation.