在解一些含多个字母的二次多项式的因式分解题时，我们可以考虑选择其中一个字母作为主元，那么已知多项式可整理成关于主元的二次三项式，然后利用十字相乘法进行分解，这种分解因式的方法称为主无法．下面举例介绍它的具体应用‘例1分解因式：x’～a’－Zx—Za·解以X为主元 When solving a factorization problem for some polynomials with multiple letters, we can consider selecting one of the letters as the pivot element. Then the known polynomial can be organized into a quadratic trinomial about the pivot element, and then use the cross. Multiplicative decomposition, this decomposition factoring method is called master can not. The following is an example to introduce its specific application. 例 Example 1 factorization factor: x’~a’-Zx—Za· solution to X as the primary element