321.sagews

x, y, z, u, v,= var('x,y,z,u,v')

plot3d((x^2)*(y^2)/(x^2+3*y^4), (x,-7,7), (y,-5,5))

plot3d((x^3)*(y)/(x^6+y^2), (x,-7,7), (y,-5,5))

fx = u
fy = (1/2)*u^2
fz = (1/3)*u^3
parametric_plot3d([fx, fy, fz], (u,-7,7), color='green')

plot3d((x^2) - (y^2), (x,-4,5), (y,-5,5))