The "main" vertices are on the y-axis, so the minor vertices are on the x-axis. This ellipse has center on the origin. This is known because the denominators of 8 and 4 are of the order . The larger denominator identifies the major axis. The minor axis is also the one which contains the co-vertices. Your example has or 2 for the distance from center to either co-vertex, so the co-vertices are (-2,0) and (2,0).