Arithmetic series
等差级数
🧩 词语组成解析
🗣️ 情景例句
How are you getting along?
近来如何？
An old poacher makes the best keeper.
老偷猎者是最好的看守人。
the bank and its customer owe a large number of obligations to one another.
银行和储户彼此还需承担大量义务。