powder series的用法和樣例：
例句
- The process of replacing polynomials by formal power series is an example of a general device known as completion.
用形式冪級數來代替多項式的過程是被稱之為完備化的這種一般手段的一個例子。 - To terminate a computational process in accordance with some rule, e.g., to end the evaluation of a power series at a specified term.
根據某種規則終止一個計算過程，例如，對冪級數估值時，取到指定項就停止運算。
