Definition:

Slope

The steepness of a line. The ratio of the vertical change to the horizontal change.

	Lines that go uphill (from left to right) have Positive Slopes	If point 1 is to the left and point 2 is to the right, the rise would be positive and the run would be positive. A positive divided by a positive is a positive. If point 1 is to the right and point 2 is to the left, the rise would be negative and the run would be negative. A negative divided by a negative is a positive.
	Lines that are horizontal have a: Zero Slope	The difference between the two y-coordinates would be zero.  The difference between the two x-coordinates would be some number other than zero. Zero divided by a non zero number is zero.
	Lines that go downhill (from left to right) have: Negative Slopes	If point 1 is on the left and point 2 on the right, then the rise would be negative and the run would be positive. A negative divided by a positive is a negative. If point 1 is on the right and point 2 on the left, then the rise is positive and the run would be negative. A positive divided by a negative is a negative.
	Vertical lines have an: Undefined Slope	The rise will be a non-zero number, and the run will be zero. Any number divided by zero is impossible or undefined.

Example: What is the slope of the roof of the building shown below?

Another way to think of the slope formula is "Rise over Run" The slope of the roof is 2/5.

	Start with the Slope Formula
	Decide which point is point 1, and which is point 2, and substitute them into the formula.
	Calculate the result.

Two other important principles in this lesson:

 Definitions:

Techniques: