## Intermediate Algebra for College Students (7th Edition)

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RECALL: $\text{slope} = \frac{\text{change in y}}{\text{change in x}}$ The points on a horizontal line have the same y-value. This means that for any two given points, the change in y-value is 0. Since the numerator of $\frac{\text{change in y}}{\text{change in x}}$, for whatever value of the denominator (except 0), the slope will always be equal to 0. Thus, the slope of a horizontal line is 0.