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Sunday, February 13, 2011

Graphing Linear Equalities using slope-intercept form (Rise over Run)

A steep hill has a greater slope than a gradual incline.
A steep roof may rise UP 10 inches to every 120 inches across ACROSS.  This would have a slope of 10/12.  In other words, it "rises" 10 inches as it "runs" 12 inches.  This would be an extremely steep roof!  
♦ The slope is 10/12, and to make the line on a graph, you would use rise over run.  You would start at 0 in the center of your graph having an x and y axis (see videos below), and rise 10, then run 12.  Draw a point here, then draw a line connecting this point to 0 on your graph.
♦ A more gradual incline (a less steep roof) might have a slope of 5/12.
This slope is called the pitch of the roof.  You must know what pitch you need when ordering tresses for a roof.

(1) - graphing a slope

(2) - graphing slope-intercept form
At this stage, you are not asked to identify what x and y specifically equal.  They actually equal all points along the line that was graphed.  
To determine specifically what x and y equal, you would need 2 equations, called a system of equations.  Where the 2 graphed lines intersect will be your answer.

(3), converting to slope-intercept form; graphing

This method is called Slope-Intercept because it is graphed by first finding the point where the line will intercept the y-axis, and then finding the slope of the line using "rise over run" -- the number beside x in the equation.

►'s Demo Lesson just happens to be about slope-intercept.  =)  These slopes are already graphed, and you learn how to figure the slope.
Click on Demo Lesson under the video.  The explanation is fast, but there is a help button. 

There are 4 videos for 4 example problems.
Then click on the buttons for the practice problems, and see if you know the answers.
Below the practice problem buttons, you can click to see a hint, or the answer, as well as show an explanation.
The volume icon gives an oral explanation of the practice problem you are on.
There is also a self-test. Click the problem number 1.  Click on MC to see the multiple choice answers.  Choose A, B, C, or D.
If you click on the wrong answer, you can click on the Notepad icon for an explanation.

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