Question
Form the differential equation representing the family of ellipses having foci on x-axis and centre at the origin.
Solution
The general equation of such ellipse is
...(1)

Differentiating w.r.t. x successively two times, we get.
...(2)
...(3)
and
...(4)
From (3), (4), we get

which is the required differential equation.


Differentiating w.r.t. x successively two times, we get.


and

From (3), (4), we get

which is the required differential equation.