13.6 Graphing Linear Equations Objective: Graph linear equations using both the intercept method and slope-intercept form.
Example 1-Standard Form • Ax + By = C • A and B can not both be zero…why? • Put the following equation in standard form: 2x = 3y + 12
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Example 2 – Intercept Method • Graph the line 2x – 3y = 12 using the Intercept Method. • Find the x and y intercepts • Points where the line crosses the x and y axes. • Solve for x = 0 and y = 0. 12/28/12
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Example 3 • Use algebra to find the intersection of the following lines: • 2x – 3y = 9 • 4x + y = 4
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Example 4 - Slope–Intercept Form • y = mx + b • m = slope • b = y-intercept • Put the following equation in slopeintercept form: • 4x + y = 4 12/28/12
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Example 5 3 • Graph the line: y = − x + 6 4
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13.7 Writing Linear Equations • Objective: Write linear equations using both the slope-intercept and the pointslope formulas.
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Example 1 • Write the equation (in slope-intercept form) of each line described. • A) slope = -5/3 and y-intercept = 4 • B) x-intercept = -6, y-intercept = 3
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Point-Slope Formula • (y –y1) = m(x – x2) • You only substitute values in for m, x1 and x2. • (x1, x2) is any point on the line.
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Examples 2-5 • For the following 4 examples, write the equation of each line described: • 2. Contains the point (5, -2) and has a slope of 2.
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Example 3 • Passes through (-3, 0) and (1, 8)
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Example 4 • Line through (1, 2) and parallel to the line y = 3x - 7
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Example 8 • Line through (1, 2) and perpendicular to the line y = 3x - 7
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Homework… • Bring textbook tomorrow!
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