为了令你们习惯于这个想法，我画一个三变量函数的等值面,这是一个平面,由函数w=c给出的。

So, just to get you used to this idea, I'm going to draw a level surface of a function of three variables OK, so it's a surface given by the equation w of x, y, z equals some constant c.

youdao

为了令你们习惯于这个想法，我画一个三变量函数的等值面,这是一个平面,由函数w=c给出的。

So, just to get you used to this idea, I'm going to draw a level surface of a function of three variables OK, so it's a surface given by the equation w of x, y, z equals some constant c.

youdao