"For those who wish to become citizens, we should require them to pay a penalty and pay taxes, learn English, go to the back of the line behind those who played by the rules.

VOA: standard.2009.06.19

x and y can be whatever you like, but I picked a very special example You should go back and remember what we did.

你可以任意选取 x 和 y,但我这里讲个特例,你们应该回忆一下上节课的内容

耶鲁公开课 - 基础物理课程节选