在高考复习中,常涉及到极值点相关的证明问题,也即求导后的导函数的零点相关的证明问题.而在实际操作过程中,求导后往往含参数或超越方程,直接处理起来较为复杂.一般地,此类题目往往通过适当的换元途径可获得良好的解题效果.下面就几种常见换元途径整理如下,供参考.1参数变换为零点——客变主,暄宾夺主例1(2017届湖北重点高中协作体期中考试)设函数f(x)=x~2-bx+alnx,(1)若b=2,函数f(x) In the college entrance examination review, often involves the extremum points related to prove the problem, that is, after derivative of the derivative of the derivative of the zero-point proof.In the actual operation, after the derivation often contain parameters or transcendental equations, direct processing In general, these topics are often available through the appropriate way to change yuan meticulous problem-solving effect. Here are some common ways to change the yuan as follows, for reference .1 parameter conversion to zero - the main customer change, (1) If b = 2, the function f (x) = x ~ 2-bx + alnx