怎样去解一个一次方程组?一个很自然、也是很重要的想法,是把这一问题转化为我们已经熟悉了的问题——解一元一次方程.于是,就必须在方程组中消去一个未知数,即消元.为贯彻“消元”的思想,课本介绍了两种基本方法,即代入法和加减法.下面谈谈如何活用代入法和加减法进行消元. How do we solve a system of equations? A very natural and important idea is to turn this problem into a problem that we are already familiar with - solving a one-dimensional equation. Then we have to eliminate an unknown in the system of equations. That is to eliminate the Yuan. In order to carry out the idea of ​​“elimination of Yuan,” the textbook introduces two basic methods, namely the substitution method and addition and subtraction. The following talks about how to use the substitution method and the addition and subtraction to eliminate the element.