The essence of cross multiplication is a form of simplifying equation, and quadratic trinomial can be factorized, but we must pay attention to the sign of each coefficient. The method of cross multiplication is simply: the left multiplication of the cross is equal to the quadratic term, the right multiplication is equal to the constant term, and the cross multiplication and addition is equal to the linear term. In fact, it is to use the multiplication formula (x+a)(x+b)=x? +(a+b)x+ab for factorization.

Methods/steps

Define the concept and core of cross multiplication.

Let's look at this multiplication formula (x+a)(x+b), and we can easily get (x+a)(x+b)=x? +(a+b)x+ab. Now turn it upside down.

Break it down like this, how to write the result? Let's keep watching x? Factorization of +(a+b)x+ab.

If the quadratic coefficient is not 1, how to decompose it? Let's look at this example.

Let's take a look at the application of cross multiplication in factorization.

Understand the application of cross multiplication in solving equations.

seven

Cross factorization can simplify our calculation, which is a very practical method. But not all factorization can be done by cross multiplication. We should accumulate experience in the process of doing the problem and judge whether this method can be used as soon as possible.