utility function的用法和樣例：
例句
- In the first part of this paper, we introduce briefly the background and recent research of recursive utility.
本文第一章首先對遞歸效用函數的背景及研究近況作了一個簡要的介紹。 - So people begin to find out if there is another utility which is more practical and less complicated.
於是，人們開始研究是否有其他更切合實際但又不至於過分複雜的效用函數。
