Quadratic Graphing Calculator

This draws the parabola for a quadratic and works out every feature of it exactly. Enter a, b and c, or the vertex form a, h and k, and it returns the vertex, the axis of symmetry, the completed square, both intercepts, the discriminant, the focus, the directrix and the focal width, with a plot that marks each of them. The window is chosen to show the vertex, the roots and the y-intercept unless you set your own. The values come from the algebra rather than from reading the curve, so a vertex at minus two thirds is reported as such and not as a point near the bottom of the graph.