elliptic curves plot

edit

The legend shows the functions twice. I don't like that. How can I change it, that the function is only once showed? Thank you :)

code:

p=plot(EllipticCurve([0,0,0,3,0]), gridlines='true', color=hue(0.7),xmin=-4, xmax=4, ymin=-3, ymax=3, legend_label='$y^2=x^3+3x$')
p+=plot(EllipticCurve([0,0,0,2,0]), gridlines='true', color='cornflowerblue',xmin=-4, xmax=4, ymin=-3, ymax=3, legend_label='$y^2=x^3+2x$')
p+=plot(EllipticCurve([0,0,0,1,0]), gridlines='true', color='red',xmin=-4, xmax=4, ymin=-3, ymax=3, legend_label='$y^2=x^3+x$')
p+=plot(EllipticCurve([0,0,0,-1,0]), gridlines='true', color='orange',xmin=-4, xmax=4, ymin=-3, ymax=3)
p+=plot(EllipticCurve([0,0,0,-2,0]), gridlines='true', color=hue(0.2),xmin=-4, xmax=4, ymin=-3, ymax=3, legend_label='$y^2=x^3-2x$')
p+=plot(EllipticCurve([0,0,0,-3,0]), gridlines='true', color=hue(0.3),xmin=-4, xmax=4, ymin=-3, ymax=3, legend_label='$y^2=x^3-3x$')
p+=point((-3,0), color='white', legend_label='$y^2=x^3-x$')

p.set_legend_options(shadow=False, loc=2)
show(p)
p.axes_labels(['$x$','$y$'])
p.save('Einleitung2.pdf')