求函数的值域是函数一章的重要问题,也是高考命题的热点.求函数的值域除常用一些基本方法外,还必须掌握一些技巧,现归纳、总结如下:1.用x的表达式的性质在用反函数法求函数的值域时,不求出x,而是求x的表达式,用表达式的性质求值域,可简化运算.例1求下列函数的值域:(1)y=1-x21+x Find the value range of the function is an important chapter of the function, but also hot topic of the college entrance examination. In addition to the commonly used method of value range some basic methods, but also must master some skills, are summarized as follows: 1. The nature of the formula In the use of inverse function method to find the value of the domain, do not find x, but the expression of x, the nature of the expression domain, simplifying the operation Example 1 The following function range: (1) y = 1-x21 + x