Algebra is a branch of mathematics that studies numbers, quantities, relationships and structures. Elementary algebra is generally taught in middle schools, introducing the basic ideas of algebra: studying what happens when we add or multiply numbers, understanding the concept of variables and how to establish polynomials and find their roots. The research object of algebra is not only numbers, but various abstract structures. For example, an integer set is an algebraic structure as a set with addition, multiplication and order relations. Among them, we only care about various relationships and their nature, but we don't care about the question "what is the number itself". The common types of algebraic structures are groups, rings, fields, modules, linear spaces and so on. Algebra is one of the most important and basic branches of mathematics. Algebra has a long history. It comes into being and develops with the improvement of human living standard, the progress of production technology and the needs of science and mathematics itself. In this process, the research objects and methods of algebra have changed greatly. Algebra can be divided into elementary algebra and abstract algebra. Elementary algebra is the extension and development of older arithmetic, while abstract algebra is produced and developed on the basis of elementary algebra. Elementary algebra refers to the theory of equations before the first half of19th century. It mainly studies whether an equation (group) is solvable, how to find all the roots (including approximate roots) of the equation and various properties of the roots of the equation.