Its essence is to use real number operation to define the size relationship between two real numbers. It is the basis of this chapter, and it is also the main basis for inequality and solving inequality.

We can combine the familiar knowledge background of monotonicity of functions and realize that the theoretical basis of difference ratio is the nature of inequality.

After the difference, in order to judge the sign of the difference, it is necessary to decompose the factor in order to make use of the sign law of real number operation.

The formula that uses the symbol ">" "< to represent the relationship between size is called inequality. An inequality represented by "≦" is also an inequality. ?

Numbers in general inequalities are real numbers, and letters also represent real numbers. The general form of inequality is F(x, y, ..., z)≤G(x, y, ..., z? ) (in which inequality symbols can also be one of them), the common domain of analytical expressions on both sides is called inequality domain, which can represent both a proposition and a problem.