?ContourPlot

Ellipse = ContourPlot[ x^2/4 + y^2 == 1, {x , -2, 2}, {y, -2,2} ]

Hyperbel = ContourPlot[ x^2 - y^2 == 1, {x , -2, 2}, {y, -2,2} ]

Show[ Ellipse, Hyperbel]