利用复合函数求导规则：u=x²y，v=x³+y³，∂u/∂x=2xy,∂u/∂y=x²，∂v/∂x=3x²，∂v/∂y=3y²；z=y³/2x+f（u，v）∂z/∂x=-y³/2x²+∂f/∂u.∂u/∂x+∂f/∂v.∂v/∂x=-y³/2x²+2xy∂f/∂u+3x²∂f/∂v
