导数题中有很多要用到构造函数的方法解题,而换元构造法又是导数题中的难点,但是只要我们认真总结此类题的解题思路和方法,就不难发现其中的规律,从而让我们对此类题有了更清晰的认识,在解题时更加得心应手.例1已知函数f(x)=xlnx(x>0),其导函数为g(x),A(x_1,y_1),B(x_2,y_2)为曲线y=g(x)上的两点,且0 There are a lot of questions in the derivative problem that need to use the constructor function, and the construction method of the replacement element is also a difficulty in the derivative problem, but as long as we seriously summarize the problem-solving ideas and methods of such problems, it is not difficult to find the laws Therefore, let us have a clearer understanding of such questions, in the problem solving is more handy. Example 1 Known function f (x) = xlnx (x> 0), its derivative function is g (x), A ( X_1,y_1),B(x_2,y_2) are two points on the curve y=g(x), and 0