与三次函数有关的问题常常在高考试题和竞赛试题中出现 ,原因有二个 ,其一是教材上虽然没有介绍三次函数的一般性质 ,但是可以借助初等方法进行研究 ;其二是随着新教材的使用和推广 ,可以用导数为工具来研究三次函数的某些特征 ,因此 ,三次函数必然成为考试的热点问题 .我们知 Questions related to cubic functions are often found in high test questions and competition test questions for two reasons. First, although the general nature of the three functions is not introduced in the teaching materials, they can be studied with the aid of elementary methods; secondly, with the new textbooks. The use and promotion of the method can use derivatives as a tool to study some features of the cubic function. Therefore, the cubic function must be a hot issue of the exam.