所谓双函数,即问题涉及两个函数,而且一般来讲,两个函数总是相互制约的.解这类问题,需要综合运用函数知识,同时还要善于抓主要矛盾或者说是利用主要条件.下面分类解读双函数问题. The so-called double function, that is, the problem involves two functions, and in general, the two functions are always mutually restrictive. To solve such problems, we need to comprehensively use the knowledge of the function, but also be good at grasping the main contradiction or to use the main conditions. The following classification explains the double function problem.