You may want to review equations of ellipses centered at the origin first.

Ellipses can be centered at any point, not just at the origin. In
that case, the equation will look like (*x* −
3)^{2} / 289 + (*y* − 4)^{2} / 49
− 1 = 0. Just like with a circle, the center is (3, 4). (As
with a circle, remember that the signs are switched from what they
are in the equation.) Just like an ellipse centered at the origin,
the horizontal radius is 17 (the square root of 289) and the
vertical radius is 2 (the square root of 4).