求函数值域是中学数学的一个难点,学生表现的突出心理障碍,一是方法无规则难以把握,二是思维无形象无所适从。现介绍一种有效求函数值域的方法———数形结合转换模式求函数值域。设u(x)、v(x)是关于x的函数,F(u,v)=0是常见的曲线,则对于函数y=f(x)的值有下述结论:(1)若y=u±v则y是关于u、v的直线的截距或是两线段的 Seeking the function value domain is a difficult point of middle school mathematics. The outstanding psychology obstacle of students’ performance is that one method is difficult to grasp without rules, and the other is that there is no image at a glance. Now introduce an effective method for the value of the domain method --- number form with the conversion mode for the function value range. Let u (x), v (x) be a function of x and F (u, v) = 0 be a common curve. The following conclusions can be drawn for the value of the function y = f (x): (1) If y = u ± v Then y is the intercept of the straight line of u, v or two-line segment