Answer:
There are four type of conic generated when a double napped cone is cut by a plane
1.Circle
2.Parabola
3.Ellipse
4.Hyperbola
Among these four, Hyperbola is the conic , ,all points in a plane where the difference between the lengths of segments x and y remains constant.
A point on Semi major Axis=(a,0),lying on the Hyperbola.
A point on Semi Minor axis =(0,b),not lying on the Hyperbola.
Take a point D lying on the hyperbola,and two points M and N not lying on the hyperbola.
DM-DN=2a(Length of major axis)