求z=xy/(x-y)的全微分,
问题描述：
求z=xy/(x-y)的全微分,
我是怎么都做不出和答案一样的了.为什么呢,那位亲帮我做下详细过程吧,
答
z=xy/(x-y)dz=f'x(x,y)dx+f'y(x,y)dyxy/(x-y)对x取偏导得[y(x-y)-xy]/(x-y)²dxxy/(x-y)对y取偏导得[x(x-y)+xy]/(x-y)²dy所以dz=[y(x-y)-xy]/(x-y)²dx+[x(x-y)+xy]/(x-y)²dy dz=-y²/(x-y)&s...