求函数最值和值域的基本方法是由定义域出发,利用基本函数的值域、不等式的性质、导数的方法等;若将函数解析式看成关于自变量的方程,则可以从方程有解出发;若将函数解析式看成变量的关系等式,则可以从一个变量的已知取值范围求出另一个变量的取值范围.相对于求定义域而言,求值域的方法更加灵活多变,不易掌握.我们知道只含一个自变量的函数的最值问题可以通过很多种方法得到,如:观察 The basic method of finding the most value and the range of the function is to start from the domain, use the range of the basic function, the nature of the inequality, the method of the derivative, etc. If we regard the function analytic as the equation about the independent variable, Solution to the problem; if the function analytic equation as a variable relationship equation, you can get from a known value range of a variable to obtain the value of another variable. Relative to the definition of domain, the method of evaluating the domain More flexible, not easy to grasp.We know that the value of a function containing only one independent variable can be obtained by a variety of methods, such as: observation