It's kind of like , where you had side A,side B and you just flipped it over when you wanted to change your mood so to speak.

VOA: standard.2010.06.18

So I took this to the other side and I divided through by 2b and the b here cancels.

通过移项和通分成2b,就可以消去b了

耶鲁公开课 - 博弈论课程节选