F(x,y,z)=z+2xy-e^z-3∂F/∂x=2y ∂F/∂y=2x ∂F/∂z=1-e^z在(1,2,0),∂F/∂x=4 ∂F/∂y=2 ∂F/∂z=0故法线方程为：(x-1)/4=(y-2)/2=z/0
