Average Rate of Change of a Curve

Average Rate of Change of a curve is leads into the discussion of Secant Lines and the Slope of a Curve at a point. You can move the point A on the curve, move the slider h to change the difference between -1.5 and 1.5, and you may modify the function f(x) as you chose. The applet displays the slope of the line AB. When the difference reaches zero, explain what happens.