Understanding Slope Intercept Form

GeoGebra Unit.


Goal

Students will be able to explain how changing the y-intercept and slope  will change the appearance of the line.


Lesson

1) Have students write down the equation for slope intercept form and review what the m and b stand for.

2) Have students go to the following site on their computers or phones.

http://www.oercommons.org/courses/slope-intercept-form/view

3) Have students play with moving the m first. Then discuss what changed in the line when you moved the slope.

4) Then have them move just the b. Discuss what changed in the line for the y-intercept.

5) Have students find these equations and describe how the line appears. (uphill, downhill, flat, above the origin, on the origin, below the origin.)

y = 3x                     y = 2x - 1                    y = 2.5x + 3                    y = x                        y = 2              y = -3x + 4             y = 2.3x - 2                 y = -5                              y = -4x + 4              y = -2x

6) Discuss proportional and non-proportional.  Have students determine which equation were each.

7) How do you know without graphing if the line will go downhill? uphill? flat?   (negative slope, positive slope, zero slope)  (Note to teacher- it will not go to an undefined slope. You could add that to it yourself in a discussion.)



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