Whereas, at the beginning, the mortgage balance is dropping only very slowly because you've got a lot of interest to pay and your mortgage payment is constant.

而在贷款初期,贷款余款减少的则非常缓慢,这是因为还款额是固定的,同时你还要偿付大量的利息

耶鲁公开课 - 金融市场课程节选

At every point of time your mortgage balance is equal to your mortgage payment times that square bracketed thing, where T is the amount of time you have left.

在每个时间点的抵押贷款余额,都等于每月偿还额乘以,方括号内的值,T是剩余年份数

耶鲁公开课 - 金融市场课程节选