Section 1-2:   Slopes of Lines 
Demo: Slope (Utah State University)
Demo: Slope - Intercept Form (Utah State University)
Demo: Point-Slope Form (Utah State University)
As you recall from basic algebra, the slope of a non-vertical line measures the steepness of the line as related to the x-axis.  If two points are on the same line then the definition of slope is as follows:
Important facts about slope!!
Demo: affect of Slope on a line

Sample graphs of slope!
Note:  The blue line has a positive slope because it goes uphill from left to right.  The red line has a negative slope because it goes downhill from left to right.  The purple line has an undefined slope because it is vertical.  The green line has zero as the slope because it is horizontal.

Important facts about slope to remember!  

Sample problems