And our job is to find out what is the mathematical description of this path, this line in p-V's case that connects these two point.

我们的任务,就是找出，描述这条曲线的方程。

麻省理工公开课 - 热力学与动力学课程节选

And the point is that the second derivative of A, with respect to V and T in this order is the same as the second derivative of a with respect to T and V in this order.

问题的关键在于A的二阶导数，对V和T以这样一个顺序求导,和对T和V以这样一个顺序,求导是一样的。

麻省理工公开课 - 热力学与动力学课程节选