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Notes: Lesson 5-4B

Notes: Lesson 5-4B. Objective: Write an equation for a line given two points. Wait a second…. What two things do we need to write an equation for a line?. m or slope b or y-intercept. Steps:. Calculate the slope of the line. Write y = mx + b

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Notes: Lesson 5-4B

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  1. Notes: Lesson 5-4B Objective: Write an equation for a line given two points Wait a second…. What two things do we need to write an equation for a line? • m or slope • b or y-intercept

  2. Steps: • Calculate the slope of the line. • Write y = mx + b • Fill in the slope (m) and the coordinates of one of the given points (x, y) • Solve to find b • Write the equation using m and b Only one change from yesterday!!!!

  3. x1 y1 x2 y2 Write the equation for the line that passes through (1, 3) and (-3, -5) Calculate the slope: m = -5 – 3 -3 – 1 m = -8 -4 m = 2 Find the y-intercept using: m = 2 (1, 3) y = mx + b 3 = 2(1) + b 3 = 2 + b -2 -2 1 = b Write the equation: m = 2 b = 1 y = 2x + 1

  4. x1 y1 x2 y2 Write the equation for the line that passes through (4, -1) and (-4, 5) Calculate the slope: m = 5 – (-1) -4 – 4 m = 6 -8 m = - ¾ Find the y-intercept using: m = -¾ (4, -1) y = mx + b -1 = -¾(4) + b -1 = -3 + b +3 +3 2 = b Write the equation: m = - ¾ b = 2 y = -¾ x + 2

  5. x1 y1 x2 y2 Write the equation for the line that passes through (0, - 4) and (5, 2) Calculate the slope: m = 2 – (- 4) 5 – 0 m = 6 5 m = 6/5 Find the y-intercept using: m = 6/5 (0, - 4) y = mx + b - 4 = 6/5(0) + b - 4 = 0 + b - 4 = b Write the equation: m = 6/5b = - 4 y = 6/5x - 4

  6. Did you master the objective? • Then prove it… • Try the following problem by yourself then check your work with your neighbor.

  7. Write the equation for the line that has an x-intercept of 4 and a y-intercept of -7 (4, 0) and (0, -7) Calculate the slope: m = - 7 – 0 0 – 4 m = -7 -4 m = 7/4 Find the y-intercept: b = -7 (given!) Write the equation: m = 7/4 b = -7 y = 7/4 x -7

  8. 5.4B assignment page 284 #20-32 even Work must be shown!

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