• Move the slider to change the value of $A$, $B$, or $C$.
• Check the box to see a second point and the related arrow on the mapping diagram and triangle on the graph that illustrates the "slope" of the secant line when $\Delta x = 1$. Notice the connection between this slope and $A$ when $x = -\frac B {2A}$.
• Select the point $x$ in the mapping diagram to move the point by mouse or use the scroll up or down key  to move by increments of 1.
  

Martin Flashman, Oct. 25, 2013, Created with GeoGebra