The *vertex* of a parabola is the point at which the parabola itself intersects its axis of symmetry, the line that divides it in half. For parabolas that open upward, the vertex is the lowest point on the curve, the minimum. For parabolas that open downward, the vertex is the highest point on the curve, the maximum.

If the coordinates of the vertex of a parabola are *vertex form* as:

where

is a constant. If , the parabola opens upward, and if , it opens downward.