Let's say you have to go through three or four operations to get a final number, well, do it algebraically.

让我们说,你不得不通过3-4个操作,才能得到最终的数，好吧，用代数方法求解。

麻省理工公开课 - 固态化学导论课程节选

You add them all up algebraically, keeping track of their sign, and that's the total force.

你再对这些力做代数加法,注意符号,就求出合力了

耶鲁公开课 - 基础物理课程节选