The slope of a straight line is calculated by dividing its rise by its run. Each point on a line has both a "y" coordinate, which corresponds to the line's vertical place on a graph, and an "x" coordinate, which corresponds to the line's horizontal place on a graph. To find the slope, choose any two points on the line. The line's rise is equal to the difference between the two "y" coordinates, and its run is equal to the difference between the two "x" coordinates. After this fraction is in place, you can determine if the slope is undefined.
Instructions
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1
Reduce your slope's fraction. For example, if the rise is equal to (-4) - (2) and the run is equal to (1) - (1), the fraction would be -6 over 0. If the denominator of the slope is 0, as it is in this example, the slope is undefined.
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2
Look at the line on a graph. If the graph shows a vertical line that goes straight up and down, its slope is undefined.
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3
Review the x-coordinates of the points on the line. If all of the x-coordinates are identical, then the equation for the slope of the line will be over 0 and, therefore, undefined.