求形如 f (x) =ax + b + d -cx(a0 ,c 0 ,dc-ba)的函数值域的方法很多 ,本刊文 [1]利用“双换元法”给出一种求法 ,阅后深受启发 .本文再给出此类函数的一种新的求法 ,具有简单易行的特点 ,更易为广大中学生所理解和接受 ,现介绍如下 .1　结论及证明定理　设 f1 (x) =ax + b There are many ways to find the range of functions such as f (x) = ax + b + d -cx (a0, c 0, dc-ba). This article [1] gives a kind of method using the “double substitution method”. The method of seeking is deeply enlightened after reading. In this paper, a new method for such functions is given, which is simple and easy to understand and easier for the majority of middle school students to understand and accept. Now it is introduced as follows. 1 Conclusion and proof Theorem Let f1 ( x) =ax + b