三次方程交汇了函数、不等式、方程等众多知识点 ,以它为载体的试题 ,背景新颖、独特 ,选拔功能强 .由于三次函数的导数为二次函数 ,因此 ,以导数与极限为工具 ,用二次函数知识对三次函数的性态进行研究 ,利用三次函数的性质和图象 ,就能巧解三次方程的有关问题 .先来研究三次 The cubic equation meets many points of knowledge such as functions, inequalities, and equations. The questions that use it as a vector have a novel and unique background and a strong selection function. Since the derivative of the cubic function is a quadratic function, the derivative and the limit are used as tools. The knowledge of the quadratic function studies the behavior of the cubic function. Using the properties and images of the cubic function, the problem of the cubic equation can be solved. First, study three times.