I looked all over the internet and could not find a parametric equation for this shape. You can look at the link below to find the regular cartesian equation. If you are good at parametric equations you could probably convert this into parametric form. I am not so good at parametric equations.

If you have two equations give AND one parametric equation why do you need to find yet another equation?

A parametric equation is a way of representing a set of points. For instance, the (x,y) co-ordinates of a certain collection of points in the plane might be given by the parametric equation,

x = 4 + t, y = 5t

where t is called the parameter of the parametric equation and ranges over the entire set of real numbers.

In this case the set of points is a line. Usually parametric equations are used to discuss curves of one kind of another.

Please see the link.

b2y2 = x3(a-x)

Parametric equations are a way of expressing the points of a curve as the function of a set parameter. Any game that displays modern scaling graphics using a form of parametric equation.