恒成立问题是高考常见题型,主要涉及函数的性质、图像,渗透着换元、化归、数形结合、函数与方程等思想方法,在培养思维的灵括性、创造性等方面起到了积极的作用。本文对常用的几种方法,进行剖析,供读者参考。一、函数性质法运用导数工具,直接求得函数最值,从而简化不等式,求得结果。特别地,对定义域为一切实数的二次函数,可 The problem of the establishment of a permanent college entrance examination is a common type of question, mainly related to the nature of the function, the image, permeated with the yuan, the return of the number of forms, functions and equations and other methods of thinking in the cultivation of spirituality, creativity has played a positive Role. In this paper, several commonly used methods for analysis, for readers reference. First, the functional nature of the law using derivative tools, the direct value of the function, thus simplifying the inequality and finding the result. In particular, for the quadratic function whose domain is all real numbers,