所谓“主元法”,就是在处理含有多个变量的数学问题时,把某个“元”看得特别重些,给以特殊的地位,不妨称这个“元”叫“主元”。在解题时,运用“主元法”’可以将一个非基本问题,化归为一个简单的、易于解决的普通问题。请看下面的例子: 1.在因式分解中的应用 例1 分解因式 x~2y~2-5x~2y-3xy~2+15xy-14x~2+5y~2+42x-25y-70. The so-called “principal element method” is to treat a “meta” as particularly important when dealing with mathematical problems involving multiple variables. Given a special status, it may be appropriate to call this “yuan” a “principal element.” When solving problems, the use of the “primary law” can be used to classify a non-essential issue as a simple, easy-to-solve common problem. Please see the following example: 1. Application in factorization Example 1 Decomposition factor x~2y~2-5x~2y-3xy~2+15xy-14x~2+5y~2+42x-25y-70.