Multiplication of algebraic expressions includes multiplication of monomial and monomial, multiplication of monomial and polynomial, and multiplication of polynomial and polynomial. The arithmetic of multiplying a monomial with a monomial. When a monomial is multiplied, its coefficients are multiplied by the same letter respectively. For a letter contained only in a monomial, it is used as a factor of the product together with its index. When multiplying a monomial with a polynomial, we should pay attention to the following points: 1. When a monomial is multiplied by a polynomial, the product is a polynomial with the same number of terms as the polynomial. 2. Pay attention to the sign of the product when operating, and each term of the polynomial contains the sign before it. 3. When mixing operations, pay attention to the operation sequence.

In the second chapter of mathematics in the seventh grade of junior high school, we learned the addition and subtraction of algebraic expressions, which laid the foundation for the next chapter to learn the linear equation with one variable. The eighth grade mathematics chapter 14 learned the multiplication of algebraic expressions, which laid the foundation for later learning fractions. The multiplication of algebraic expressions is an operation based on the operational nature of power and the distribution law of multiplication, which is the basis of learning mathematical knowledge in the future and needs students to master.