In polynomials, terms with the same letters and degrees are called similar terms. Such as 4y and 5y, 100ab and 14ab, 6c and 6c. In addition, all constant terms are similar terms (constant terms are also called digital factors).

When calculating the value of algebraic expression, similar items are often combined first, and it is easier to simplify algebraic expression and then evaluate it.

Single item:

An algebraic expression consisting of the product of numbers and letters is called a monomial, and a single number or letter is also called a monomial. This noun was translated into Chinese by Li, a mathematician in Qing Dynasty, according to the concept of the original word. The numerical factor in the monomial is called the coefficient of the monomial, and the sum of the indexes of all the letters in the monomial is called the degree of the monomial. How many times is a monomial, it is called several monomials.

Polynomial:

The sum (or difference) of several monomials is called a polynomial. Each monomial in a polynomial is called a polynomial term, and the highest degree of these monomials is the degree of this polynomial. Items without letters in polynomials are called constant terms. Mathematically, it refers to the expression obtained by addition, subtraction, multiplication and power operation (non-negative integer power) of variables and coefficients.

More broadly, the sum of 1 or 0 monomials is also a polynomial. According to this definition, polynomials are algebraic expressions. In fact, there is no theorem that is valid only for narrow polynomials but not for monomials. When 0 is a polynomial, the degree is defined as negative infinity (or 0). Monomial and polynomial are collectively called algebraic expressions. Items without letters in polynomials are called constant terms. For example, 6 in 5X+6 is a constant term.

Merge of the same project: only projects of the same category can be merged. When merging, add and subtract coefficients, and the letter index remains unchanged. Combination of different projects: projects that do not belong to the same category cannot be combined. 2. Multiplication and division of numerical values.