不等式恒成立问题在高考导数题中经常出现,常用的解答方法有参数分离法和分类讨论法。分类讨论法的难点是如何展开讨论,即“分类的标准”问题。本文将对分类讨论涉及的两种常见类型“二次型”及“有界型”进行分析并提出通用解法。一、“二次型”若求导后,导函数的符号取决于其包含的一个含参二次函数时,则需要按照“二次型”进行分类讨论。 Inequality constant problem in the entrance examination often appear in the question, the commonly used methods of separation of parameters and classification method. The difficulty of the categorical method is how to start the discussion, that is, the “standard of classification” problem. This article will analyze the two common types of classification involved “quadratic ” and “bounded ” and propose a common solution. First, the “secondary type ” If asked after the derivative of the symbol depends on the inclusion of a reference quadratic function, you need to follow the “secondary type ” to discuss the classification.