How does the position of the line affect the equation of the line? What can you say about the equations of parallel lines?
Alter the positions of the line by moving the points. (Interactive)
How does the position of the line affect the equation of the line?
Now explore what happens when you have two lines.
Position the lines so that they are parallel to each other. (Interactive)
Try various arrangements.
What can you say about the equations of parallel lines?
You may want to take a look at Perpendicular Lines after this.
Age 11 to 14