d？ y/dx？ =d/dx(dy/dx)= d/dx(-Fx/Fy)

=-[Fxx * 1+Fxy *(dy/dx)-Fx(Fyx * 1+Fyy *(dy/dx)]/F？ Y (where F(x, y) is a binary function and y is also a function about x)

Then put dy/dx = -Fx/Fy into the arrangement to get the answer.

d？ y/dx？ =-(FxxF？ y-2FxyFxFy+FyyF？ x)/F？ y