Your mortgage payment is constant through time but the fraction of it that goes to paying off principal versus interest changes through time and it just changes as dictated by this formula.

抵押贷款每月还款是固定的,但是其中本金和利息的比例关系,会随时间而改变,这是由这个公式所决定的

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If X is the number of cells, then the rate of change of X, dX/dt, the rate of change of the cell population, how fast division is taking is proportional to the number of cells I have.

如果X是细胞数目,那么X的改变率就是dX/dt,就是细胞数目的改变率,分裂的速度有多快,和细胞数量呈比例关系

耶鲁公开课 - 生物医学工程探索课程节选