TeachMe Quadratics

Have you ever wondered what Quadratics are all about? This app enables you to visualise graphically what happens when you change the values of a, b and c in the quadratic equation y = ax² + bx + c. Generally the shape of the graph is a parabola. But is it always parabolic? Where does it cross the x and y axes – if at all? Where is the vertex – if there is one?