求全微分:z=x^3-4X^2+2XY-Y^2

问题描述:

求全微分:z=x^3-4X^2+2XY-Y^2

z=x^3-4X^2+2XY-Y^2 ,
dz=(3x^2-8x+2y)dx+(2x-2y)dy.