[color=#9900ff][b]What causes the slope of the line to appear purple? [/b][/color]
[b][color=#9900ff]In this applet, when the slope of the line is NON-NEGATIVE (meaning ZERO or POSITIVE), the slope is PURPLE. When the slope of a line is POSITIVE, the line INCREASES as you look at it FROM LEFT to RIGHT. When the slope of a line is ZERO, this implies the line is HORIZONTAL. [/color][/b]