Slopes of Tangent Lines

Slide the variables a, b, and c to create different parabolas. Then, slide Point A around the parabola to see various tangent lines and their slopes.

Fix Point A at any point. What do you notice about the slope of the tangent line as you adjust the value of c? At what point on the parabola does the tangent line have a slope of zero? List the equation of any parabola and a Point A such that the slope of the tangent line is 4.