> with(plots):

> implicitplot({y=2*x^2,y=2,y=1,y=3,x=1,x=sqrt(1/2),x=sqrt(3/2)},x=-0..2,y=0..4, scaling=constrained, color=black, thickness=3);

> implicitplot({y=2*x^2,y=2,y=1.5,y=2.5,x=1,x=sqrt(1.5/2),x=sqrt(2.5/2)},x=-0..2,y=0..4, scaling=constrained, color=black, thickness=3);