我们在列方程(组)解应用题时,往往误认为设几个未知数,就必须从题目中找出几个相等关系,列出几个方程,再求解,即未知数的个数应与方程的个数相同,否则就难以得到确定的解.其实未必如此.许多应用题,我们还可以利用辅助未知数来解答. When we solve problems in the equations (groups) of columns, we often mistakenly think that we need to set several unknowns. We must find several equal relations from the questions, list a few equations, and solve them again. That is, the number of unknowns should be equal to that of equations. The same number, otherwise it is difficult to get a definitive solution. In fact, this may not be the case. Many applications, we can also use the auxiliary unknown solution.