1. If the first term of the polynomial is negative, the negative sign should be extracted first;

The "negative" here means "minus sign". If the first term of a polynomial is negative, it is generally necessary to put forward a negative sign to make the coefficient of the first term in brackets positive.

2. If each term of the polynomial contains a common factor, first extract this common factor, and then further decompose this factor;

It should be noted that when the whole term of a polynomial is a common factor, 1 should not be omitted in brackets after this common factor is put forward first; The common factor should be cleaned up at one time, and the polynomial in each bracket can't be decomposed.

3. If there is no common factor, then try to decompose it by formula and cross multiplication;

4. If the above methods cannot be decomposed, you can try to decompose by grouping, splitting and supplementing.

Formula: first mention the first negative sign, then see if there is a common factor, and then see if you can set a formula, try cross multiplication and group appropriately.

Extended data:

Factorial decomposition mainly includes cross multiplication, undetermined coefficient method, double cross multiplication, symmetric polynomial method, rotational symmetric polynomial method, remainder theorem method and so on. There is no universal method to find the root common factor decomposition. The junior high school mathematics textbooks mainly introduce the methods of putting forward common factors, using formulas and grouping decomposition. There are French division, addition and subtraction, method of substitution, long division, short division, division and so on.

Principle:

1. The factorization factor is an identical deformation of a polynomial, and the left side of the equation must be a polynomial.

2. The result of factorization must be expressed in the form of product.

3. Each factor must be an algebraic expression, and the degree of each factor must be lower than that of the original polynomial.

4. In the end, only brackets are left, and factorization must be carried out until each polynomial factorization can no longer be decomposed;

5. The polynomial term of the result is generally positive. Extract the common factor from a formula, that is, recombine the formula and then extract the common factor;

6. The first coefficient in brackets is generally positive;

7. If a monomial is multiplied by a polynomial, the monomial should be mentioned before the polynomial. For example, (b+c)a should be written as A (b+c);

8. When there is no explanation for real numbers in the exam, it is generally enough to explain only rational numbers. If you have an explanation for real numbers, you usually turn to real numbers.

Formula: The first term is often negative, all terms are "public" first, and a certain term is not short of 1, and "bottom" is divided by brackets.