Suppose someone has been investing money for n years and xi is the return on the investment in a given year.

假设有人投资了n年,Xi是第i年的收益率

耶鲁公开课 - 金融市场课程节选

You pay every year a fixed amount on your house to the mortgage originator and then after so many-- n is 30 years, typically--you would then have paid it off.

你每年都在你的房子上支付一定数目的偿款,给抵押商然后,数年后,设n是30年,一般来说你已经能偿清贷款了

耶鲁公开课 - 金融市场课程节选