Systems of Linear Equations

Move the sliders a, b, c and d to explore the graphs of the linear functions y = ax + b and y = cx + d.

This is a Java Applet created using GeoGebra from www.geogebra.org - it looks like you don't have Java installed, please go to www.java.com

1. When are the graphs coinciding? intersecting? parallel?
2. Describe the relationship between the appearance of the graphs and the parameters a, b, c, and d.
3. Is it possible to adjust the sliders such that the two lines are perpendicular? Justify your answer.