简单计算一下即可，答案如图所示
设函数f(u,v)可微,求u=f(x/y,y/z) 的全微分du=f1' d(x/y)+f2'd(y/z)=f1'·(ydx-xdy)/y² +f2'·(zdy-ydz)/z²=f1'/y dx+(-x/y²f1'+1/z f2')dy-y/z²f2'dz
