定值问题是中学数学中一大知识点,也是一个难点。此类问题,分布很广,综合性强,构思精妙,形式多变。特别是一些“无关”型定值问题,进一步提高了命题中可变条件的“份量”,增加了解题的难度,学生往往感到此类问题很新颖,但如何求解却不得要领。这里想通过一些例题,说明一些方法,并对这类问题进行归纳,从而摸索出一点规律。一、与某些参数“无关”的定值问题 Fixed value problem is a major knowledge in middle school mathematics, and it is also a difficult point. Such problems are widely distributed, comprehensive, exquisite in concept, and varied in form. In particular, some “irrelevant” type valuation problems further increase the “weight” of the variable conditions in the proposition and increase the difficulty of understanding the problem. Students often find this type of problem very novel, but how to solve it is not essential. Here I would like to illustrate some methods through some examples, and generalize such questions so as to find out a little law. I. Fixed value problems that are “irrelevant” to certain parameters