This Geogebra file kindly submitted by Greg Bland dramatically illustrates that the derivative of a cubic function is a quadratic function. Sliders allow you to change the parameters of the cubic function.

Geogebra is a fantastic FREEE dynamic geometry program available from
http://geogebra.org

A collection of four Geogebra files from Greg Bland that will help students understand conics.

Geogebra is a fantastic FREE dynamic geometry program that can be downloaded from
http://geogebra.org