And so I could now make a plot x whereby I could have here x F and I could have here this force F, which I know because I know the masses.
现在我可以,画一张图,这里是,这是力，这个力我们知道,因为它就是重物质量。
Remember, partial f, partial x was obtained by y That means I am slicing the graph of f by a plane that is parallel to the x, z plane.
要记得，在这里的fx中,是作为常量保持不变的。，looking，at，the，situation，where，y，is，held，constant。,这是我用一个平行于xz坐标系的平面,横截了f，所得到的图形。
Well, the change in f is the value of f at the upper point here, which is x0+delta x, and minus its value at the lower point P, which is f of x0, divided by delta x.
f的变量就是f在上面的点时的值，x0+deltax，减去f在下面的点P时的值，x0，再除以delta x。
Namely, let's say that you have a function maybe of three variables, x, y, z, df = fxdx+fydy +fzdz then you would write df equals f sub x dx plus f sub y dy plus f sub z dz.
即是说，如果你有一个,含自变量，x，y，z的函数，那么。
Namely, let's say that you have a function maybe of three variables, x, y, z, df = fxdx+fydy +fzdz then you would write df equals f sub x dx plus f sub y dy plus f sub z dz.
即是说，如果你有一个,含自变量，x，y，z的函数，那么。
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