The graph of a quadratic function y = ax² + bx + c is called a parabola. The following graphs are two typical parabolas:

For the sake of explanation, we mark their x-intercepts by red dots, their y-intercepts by a pink dot, and the vertex of each parabola by a green dot:

To find the x-coordinate for the vertex we use the following formula:

To find the y-coordinate for the vertex we plug in h in the original equation:
k = a(h)² + b(h) + c

The x- and y-coordinates of the vertex can also be expressed as:

Where

Another name for the vertex of the parabola is “extreme point”.