What this equation merely says is that the present value of your remaining payments is always equal to the mortgage balance.

这个等式说明了,剩余偿还额的现值,就等于抵押贷款的余额

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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