导数是研究函数的有力工具.其步骤是:一求函数f(x)的导数f′(x);二解方程f′(x)=0;三根据方程f′(x)=0的解的情况(有解或无解)判定函数的单调性;四依据单调性及特殊点(如极值)描述函数的图象和性质;五根据图象和性质解决函数问题.这里面有个难点,就是用导数研究什么样的函数?同学们可能认为,问题中什么函数, Derivatives are powerful tools for studying functions. The steps are: Find the derivative f ’(x) of the function f (x); solve the equation f’ (x) = 0; (With or without solution) to determine the monotonicity of the function; four according to monotonicity and special points (such as extreme) to describe the image and the nature of the function; five according to the image and the nature of the problem to solve the function. There is a difficulty , Is to use derivative to study what kind of function? Students may think that the question of what function,