Slope of a Line
Definition of Slope
The slope of a line is the ratio of the rise to the run when moving from any
point on the line to any other point on the line. This ratio is a number that
describes the steepness of the line.
By tradition, the letter m is used to represent the slope of a line.
Definition — Slope
The slope of the line between two points, (x1, y1) and (x2, y2), is
given by
where x1 ≠ x2.
Example
Find the slope of the line through the points (-2, 1) and (3, 5).
Solution
It does not matter which point we choose for (x1, y1).
For example,
let (x1, y1) = (-2, 1) and (x2, y2)
= (3, 5). |
m |
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Substitute the values in the slope formula. |
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Simplify. |
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The slope of the line is
.
To move from (-2, 1) to (3, 5), the ratio of rise to run is
. |
We obtain the same slope if we choose
(3, 5) for (x1, y1) and (-2, 1) for (x2, y2). |
m |
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Substitute the values in the slope formula. |
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Simplify. |
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To move from (3, 5) to (-2, 1), the ratio of rise to run is
.
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