jimthompson5910

Answers: choice C) -4

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Explanation:

There are two basic ways to find the slope. 
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The first way is where we use the slope formula
m = (y2-y1)/(x2-x1)
The two points are (x1,y1) = (-1,8) and (x2,y2) = (2,-4)
Plug the coordinate of those points into the slope formula, then simplify
m = (y2-y1)/(x2-x1)
m = (-4-8)/(2-(-1))
m = (-4-8)/(2+1)
m = (-12)/(3)
m = -4

The slope is -4

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The second way is to use a more visually oriented approach.
Start at (-1,8). 
Draw a straight vertical line through this point. Then move to the point (2,-4) and draw a completely flat horizontal line through this point. 
Mark the intersection between these two lines (vertical and horizontal) as point A

Now go back to (-1,8). Count the number of spaces you must move down to go from (-1,8) to point A. You should count out 12 spaces. This is the run, which in this case is negative since we're going downhill as we move from left to right

Then count 3 spaces to go from point A to (2,-4). This is the run

Rise = -12
Run = 3
Slope = Rise/Run = -12/3 = -4

As you can probably see, this effectively mirrors some parts of the slope formula above

No matter which method you use, the slope is -4

-4 is the same as -4/1

A slope of -4/1 means we go down 4 units and then move to the right 1 unit

So that means rise/run = -12/3 is the same as saying rise/run = -4/1