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Chapter 5Writing Linear Equations A continuation of Chapter 4 Putting it all togetherFocus is on the equation vs graphing P. 283
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• Section 5.1 Write a linear equation in the Slope-Intercept Form when: given the slope and Y-intercept when: given the graph with the y-int. Remember: Slope-Intercept Form is y = mx + b, where m is the slope and b is the y-intercept.
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• Remember: Slope-Intercept Form is y = mx + b, where m is the slope and b is the y-intercept. (0,b)• y = 3/4x – 5 slope is ¾ and the graph crosses y at (0,-5)
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EXAMPLE 1 Use slope and y-intercept to write an equation Write an equation of the line with a slope of –2 and a y-intercept of 5. y = mx + b Write slope-intercept form. y = –2x + 5 Substitute –2 for m and 5 for b.
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GUIDED PRACTICE for Examples 1 and 2Write an equation of the line with the given slopeand y-intercept.1. Slope is 8; y-intercept is –7. ANSWER y = 8x – 7
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EXAMPLE 2 Standardized Test Practice Which equation represents the line shown? 2 A y=– x+3 B y = – 5x + 3 5 2 2 2 C y=– x+1 D y = 3x + 5 5 The slope of the line is rise = –2 = – 2 . run 5 5 The line crosses the y-axis at (0, 3). So, the y-intercept is 3. y = mx + b Write slope-intercept form. y=– 2 x+3 Substitute – 2 for m and 3 for b. 5 5
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EXAMPLE 3 Write an equation of a line given two points Write an equation of the line shown. Y = 4/3 x - 5
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GUIDED PRACTICE for Examples 3 and 4 3. Write an equation of the line shown. ANSWER y=– 1 x+1 2
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• New Goal Today – given the y-int. and one other point, how can you find the slope and then write the equation? (without graphing)
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• Write the equation of a line that passes through the points (4,5) (0,-2).• Find the slope using the slope formula.• Use the slope and Y-int to write the equation.
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• Write the equation of a line that passes through the points (4, -2) (0,-2).• Find the slope using the slope formula.• Use the slope and Y-int to write the equation.
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• Write the equation of a line that passes through the points (-6, -1) and (0,3).• Find the slope using the slope formula.• Use the slope and Y-int to write the equation.
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• A recording studio charges musicians an initial fee of $50 to record an album. In addition, studio time is $35 per hour.• Write an equation that gives the total cost of an album as a function of studio time (in hours)• Find the total cost of recording an album that takes 10 hour of studio time.
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