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QUIZ Have your HW out on your desk.

QUIZ Have your HW out on your desk. HW Check. y = 3/4x + 1 y = -5/3x y+2=-5/2(x – 1) or y – 3 = -5/2(x+1) y = 1/3x + 13/3 Can’t because the s lope is undefined, so the equation is x=5 20. $26 22. C . Unit 4B Day 10 . Perpendicular Lines. Perpendicular Lines.

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QUIZ Have your HW out on your desk.

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  1. QUIZ Have your HW out on your desk.

  2. HW Check • y = 3/4x + 1 • y = -5/3x • y+2=-5/2(x – 1) or y – 3 = -5/2(x+1) • y = 1/3x + 13/3 • Can’t because the slope is undefined, so the equation is x=5 20. $26 22. C

  3. Unit 4B Day 10 Perpendicular Lines

  4. Perpendicular Lines The red line is the graph of y = – 2x + 5 and the blue line is the graph of y = 1/2 x +4

  5. Perpendicular Lines • The slopes of perpendicular lines are opposite reciprocals. Their product always equals – 1 . • Perpendicular lines are lines that intersect in a right angle. (90 degree angle) • We can decide algebraically if two lines are perpendicular by finding the slope of each line and seeing if the slopes are opposite reciprocals of each other. This is equivalent to multiplying the two slopes together and seeing if their product is –1.

  6. We can find the equation of a line perpendicular to a given line and going through a given point by: a.) first finding the slope m of the given line; b.) finding the equation of the line through the given point with slope = –1/m

  7. Ex 1: Perpendicular or Not? Since the slopes are negative reciprocals of each other the lines areperpendicular.

  8. Perpendicular or Not? Ex 2: Since the slopes are not negative reciprocals of each other (their product is not -1) the lines are not perpendicular Ex 3: Since the slopes are negative reciprocals of each other (their product is -1) the lines are perpendicular.

  9. Ex 4: Write the equation… Find the equation of a line going through the point (3, -5) and perpendicular to The slope of the perpendicular line will be m = 3/2 Using the point-slope equation where the slope m = 3/2 and the point is (3, -5) we get

  10. Write the equation… Ex 5: Find the equation of the line going through the point (4,1) and perpendicular to 2x + 6y = 10 Ex 6: Find the equation of the line going through the point (-2,7) and perpendicular to

  11. HW: 4B.10 Stamp Sheet due on Monday!

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