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Math on the Mind

8 3. x y –1 –2 0 0 1 2 3 –6. x y –1 3 0 0 2 –6 3 –9. b. a. yes; –. 4 5. y = x. Math on the Mind. 1. Is each equation a direct variation? If it is, find the constant of variation. a. x + 5 y = 10 b.  3 y + 8 x = 0. no.

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Math on the Mind

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  1. 8 3 xy –1 –2 0 0 1 2 3 –6 xy –1 3 0 0 2 –6 3 –9 b. a. yes; – 4 5 y = x Math on the Mind 1. Is each equation a direct variation? If it is, find the constant of variation. a.x + 5y = 10 b. 3y + 8x = 0 no 2. Write an equation of the direct variation that includes the point (–5, –4). 3. For each table, tell whether y varies directly with x. If it does, write an equation for the direct variation. yes; y = –3x no

  2. Inverse Variation Mrs. King Algebra A Unit 7, Day 2

  3. Party Time! • Mrs. King baked cookies for her students. She has 12 students in her class, so she baked 24 cookies. • If all students are present, how many cookies does each student get?

  4. Party Time! • Mrs. King baked cookies for her students. She has 12 students in her class, so she baked 24 cookies. • A nasty cold leaves 4 students home in bed. If only 8 students are present, how many cookies does each student get?

  5. Party Time! • Mrs. King baked cookies for her students. She has 12 students in her class, so she baked 24 cookies. • 4 new students join the class. If now 16 students are present, how many cookies does each student get?

  6. Evaluating results • What happens to the number of cookies per student as the number of students increases?

  7. Vocabulary: • Inverse Variation: a function in the form xy = k or

  8. Writing the equation of an inverse variation http://www.phschool.com/atschool/academy123/english/academy123_content/wl-book-demo/ph-197s.html

  9. Suppose y varies inversely with x, and a point on the graph of the equation is (8, 9). Write an equation for the inverse variation. xy = k (8)(9) = k 72 = k xy = 72

  10. xy = k (5)(7) = k 35 = k xy = 35 Suppose y varies inversely with x and y=7 when x=5. Write an equation for the inverse variation.

  11. xy = k (2)(9) = k 18 = k xy = 18 Suppose y varies inversely with x and y = 9 when x = 2. Write and equation for the inverse variation.

  12. a. xy 3 10 5 6 10 3 Check each product xy. 3(10) = 30     5(6) = 30     10(3) = 30 Decide if each data set represents a direct variation or aninverse variation. Then write an equation to model the data. Inverse? Inverse; xy = 30

  13. y x b. xy 2 3 4 6 8 12 Check each ratio . 12 8 6 4 = 1.5 3 2 = 1.5 = 1.5 Direct? Direct: y = 1.5x

  14. Homework Inverse Variation worksheet (“Practice 5-6”)

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