在解决一些变元较多的数学问题时,我们往往感到难以下手,但当我们把这些变元中的一个当成未知数,而把其余变元当成已知数处理时,看似“山穷水尽”的问题,马上变得“柳暗花明”了。这种把变元中的某个视为未知数,其余的变量视为已知数的方法,我们称之为主元法。 When we solve some mathematical problems with a lot of arguments, we often find it difficult to start, but when we treat one of these arguments as an unknown number and treat the rest of the arguments as a known number, it seems to be a question of “doing nothing”. , it immediately became “dark and bright.” This treats one of the arguments as an unknown number, and the remaining variables are treated as known numbers. We call this the principal element method.