The Vertex is a point where two or more curve meets. In the case of a quadratic equation, the vertex is at the minimum point (if a is positive) or at the maximum point (if a is negative).
When the graph of a quadratic function crosses the x-axis twice, the x-coordinate of the vertex lies between the two x-intercepts.
Note that the two x-intercepts are the roots of the quadratic function.
The zero crossings are symmetrical about the line of symmetry, which is a vertical line through the vertex. The x-coordinate of the vertex s the average of the two x-intercepts, so lies between them--exactly halfway between them.
