And, so you propose that there is no, that this derivative is zero, and that the internal energy is given simply by this quantity.

你认为这是零，这个微分是零，内能仅仅由,这个简单的量决定。

麻省理工公开课 - 热力学与动力学课程节选

So the result is we can combine all of these as a single differential, and just like we've seen before, what that suggests is that we define another new quantity given by this expression.

结果就是我们能把所有的结果,整理成一个单一的微分，就像我们前面看到的一样，这说明我们可以利用这个式子,定义一个新的物理量。

麻省理工公开课 - 热力学与动力学课程节选

It tells me the other way around to look at how prices correspond to quantities, it tells me the quantity demanded at any given price.

它直观的显示出,价格如何与产量对应,即在给定的价格上需求量是多少

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What this really means is in a given time, the change in this quantity is a times the change in this quantity.

这里的真正含义是在给定的一段时间内,这个量的变化量等于,a乘以这个量的变化量

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And that implies that since the quantity we want is given by this quantity, which is zero times a constant, the quantity we want is also zero.

因为我们需要的量,是由这个量乘以一个常数，因为这个量是零，因此我们需要的量也是零。

麻省理工公开课 - 热力学与动力学课程节选