分类讨论思想是高中重要的数学思想,也是高考考查的重点.一、正难则反思想,有效避免讨论有时正面直接思考问题,需要分多种情况考虑.而如果考察对立面,可能情况会显得更简单,这就是正难则反的补集思想.这种思想在函数、概率等问题中很常见. Classification thinking is an important high school mathematics thinking, but also the focus of the college entrance examination examinations, one is the difficulty of anti-thinking, and effectively avoid discussing sometimes positive direct thinking, need to be divided into many situations to consider, and if you examine the opposite, the situation may be more Simple, this is the complement of ideas that are hard to resist. This idea is common in problems such as functions and probabilities.