Ancient methods of solving equations. Tianyuanshu is a solution of China's ancient polynomial equations, the earliest solution of multivariate higher-order equations in the world, and the earliest semi-symbolic algebra in the world. Tianyuan tree first appeared at the end of 12. Among the existing ancient arithmetical books, the earliest discussion on the celestial skill is "Measuring the Circle Sea Mirror" written by Ye Li in 1248 and "Yi Gu Yan Duan" written in 1259. /kloc-In the 3rd century, magic was popular in the Jin Dynasty. The art of heaven is set as an unknown in elementary mathematics, and the unknown is represented by Tianyuan. Then two equal polynomials are listed according to the given conditions, and an equation with one end equal to 0 is obtained by subtraction. In the celestial technique, the equations are arranged by calculation, and a word "Tai" is written next to the number to indicate the constant term, or a word "Yuan" is written to indicate the unknown. Celestial sphere only lists the coefficients of each term of the equation, and the number of times of each next level is higher.