Once you've got that, you can do minus 7 times a vector Just take the vector, multiply it by Pi and flip it over.

明白这点之后,你就可以计算-7乘以矢量,只需用 π 去乘以那个矢量,然后将其方向调转

耶鲁公开课 - 基础物理课程节选

So, if you can flip your lecture notes over and just write on the blank space, we're going to cover electronegativity first here, and specifically, you can go back and fill this in to your lecture 9 notes, if you want to stay organized, but I just suggest just writing it on lecture 10 notes now and going back.

因此，请大家把讲义翻到背面,就在空白处做一下笔记，我们要先讲一讲电负性，特别提醒一下，大家可以,回到第九课的讲义并把这些记在那里，如果你想保持条理性的话,但是我建议大家先写在第十课的讲义上,回去再记到第九课的讲义上。

麻省理工公开课 - 化学原理课程节选