xyz+lnx+lnz=0对x求偏导yz+xy *Z'x +1/x +Z'x /z=0那么Z'x=(-yz-1/x) /(xy+1/z)对y求偏导xz+xy *Z'y +Z'y /z=0即Z'y= -xz /(xy+1/z)所以dz=(-yz-1/x) /(xy+1/z) dx -xz /(xy+1/z)dy
