对题设条件或结论范围过宽的问题,往往需要进行分类计论,方能求解.一般说来,解题中分类讨论主要从下面三个方面考虑:按题目涉及对象的定义、性质进行分类;按解题运算法则、方法的需要进行分类;按题目的一此特殊要求进行分类.下面举例说明. For problems with too wide a range of conditions or conclusions, it is often necessary to conduct classification calculations before they can be solved. Generally speaking, the classification discussion in problem solving mainly considers the following three aspects: classification according to the definition and nature of the objects involved in the topics. According to the algorithm of the problem solving method, the need for classification; according to the topic of this special requirements for classification. The following examples illustrate.