parametrization of curves

Hello,

I have a question about parametrization of "submanifolds" or curves, respectively.

In particular in the following example:

"Let M be the set of all points which have the product of their distanes from (-1,0) and (1,0) equal 1."

Give a parametrization of M. Is M a submanifold of dimension 1?

so i thing M={(x,y): }

so i think the curve in is like two symmetric loops between .

I don't think thant M is a submanifold because of the point (0,0). But i don't know how i can parametrize M. I never have done this before. How can this be done?

Regards