220 Chapter 3 Graphing Linear Equations in Two Variables y2 y1 x2 x1 m x2 x1 0 Finding the Slope of a Line Given Two Points 11, 32 14, 22 Example 2 Find the slope of the line through the points and . Solution: To use the slope formula, first label the coordinates of each point and then substitute the coordinates into the slope formula. 5 4 y 1 11, 32 and 14, 22 1x1, y12 1x2, y22 122 132 142 112 252423 1 2 3 4 5 2221 21 22 23 24 25 Figure 3-19 x 3 2 (21, 3) (24, 22) 5 units 3 units Label the points. Apply the slope formula. Simplify to lowest terms. m y2 y1 x2 x1 5 3 5 3 The slope of the line can be verified from the graph (Figure 3-19). Answer 2. 1 6 Skill Practice Find the slope of the line through the given points. 2. 15, 22 and 11, 32 TIP: The slope formula is not dependent on which point is labeled and which point is labeled In Example 2, reversing the order in which the points are labeled results in the same slope. Label the points. 1x2, y22. 11, 32 and 14, 22 1x2, y22 1x1, y12 132 122 112 142 5 3 1x1, y12 m Apply the slope formula. Avoiding Mistakes When calculating slope, always write the change in y in the numerator. Slope Formula The slope of a line passing through the distinct points and is provided . Note: If x2 x1 0, the slope is undefined. 1x1, y12 1x2, y22
miller_beginning_intermediate_algebra_4e_ch1_3
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