复合函数的值域问题以其抽象不易理解,再加求法多,难度大,是高中数学中的难点,也是重要的考点.其实复合函数y=f[φ(x)]由内函数t=φ(x)和外函数y=f(t)复合而成的,外函数的自变量就是内函数的函数值,因此,许多复合函数的值域问题只要求出内函数的值域,再借助外函数的单调性就可轻松解决.本文仅就借助单调性求复合函数的值域做举例分析,供同学们参考. In fact, the composite function y = f [φ (x)] by the internal function t = φ (x) is the most difficult problem in high school mathematics, (x) and the outer function y = f (t), and the independent function of the outer function is the function value of the inner function. Therefore, the problem of the range of many complex functions only requires the range of the inner function, Monotonicity of the function can be easily solved.This paper only uses the monotonicity to find the value range of the composite function to make an example analysis for the students to refer to.