There is no universal method for factorization, and junior high school mathematics textbooks mainly introduce common factor method and formula method. On the other hand, there are division and addition and subtraction, grouping decomposition and cross multiplication, undetermined coefficient method, double cross multiplication, symmetric polynomial rotation symmetric polynomial method, remainder theorem method, radical method, method of substitution, long division and division.

Three principles of attention

1

Decomposition should be thorough.

2

The final result is only parentheses.

three

In the final result, the polynomial coefficient is positive (for example, -3x 2+x =-x (3x- 1).

To put it simply, the method of cross multiplication is that the multiplication on the left side of the cross is equal to the quadratic term coefficient, the multiplication on the right side is equal to the constant term, and the cross multiplication is equal to the linear term coefficient.

Cross multiplication can decompose some quadratic trinomials. The key of this method is to decompose the quadratic coefficient A into the product of two factors A 1, A2 into the product of a 1*a2, and the constant term C into the product of two factors C 1, C2 c 1*c2, and make a 1, A2+A2c/klc2.