在一些资料及试卷上常能看到如下类型的题目: 若关于x的方程(x~2-4x+a)/(x-3)=0有增根,则a=__________. 这道题给出的答案是a=3,考生也不难做出符合编题者意图的答案。 然而,这是一道给学生以错误引导、严重失误的题目,因为增根不是方程本身有没有的问题,而是在解方程的过程中,由于使用的解法扩大了未知数的允许值范围产生的。如本题中的 The following types of questions can often be seen in some materials and test papers: If the equation for x (x~2-4x+a)/(x-3)=0 has a root addition, a=__________. This question is given by The answer is a=3, and it is not difficult for candidates to make answers that meet the intention of the editor. However, this is a problem of giving students misguided and serious mistakes, because increasing roots is not a question of whether the equation itself exists, but it is in the process of solving equations, because the solution used expands the allowable value range of unknowns. As in this question