where a, b denote the semi-axes of the ellipse and denote the coordinates of the center of the ellipse.
2. The center is the midpoint of the line segment between the vertices, that means the coordinates of the center are the means of the coordinates of the vertices.
3. The distance between the center and one vertex is a.
The distance between the center and the focus is e which is calculated by:
Since you already know a and e determine b.
4. Plug in all values into the general equation of the ellipse.