15. ANSWER: –12;–12
3-4 Direct Variation
Name the constant of variation for each
equation. Then find the slope of the line that
passes through each pair of points.
Graph each equation.
17. y = –7x
ANSWER: 11. ANSWER: –5;–5
19. ANSWER: 13. ANSWER: 21. ANSWER: 15. ANSWER: –12;–12
Graph each equation.
17. y = –7x
23. ANSWER: ANSWER: eSolutions Manual - Powered by Cognero
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ANSWER: a. y = 1800x
b. 7 yr 6 mo
3-4 Direct Variation
Suppose y varies directly as x. Write a direct
variation equation that relates x and y. Then
solve.
, find x when y = 25.
31. If y = 15 when
23. ANSWER: ANSWER: y = 20x;
33. If y = –6 when x = 1.6, find y when x = 8.
ANSWER: y = –3.75x; –30
Suppose y varies directly as x. Write a direct
variation equation that relates x and y. Then
solve.
25. If y = 22 when x = 8, find y when x = –16.
ANSWER: 27. If y = 12 when
Write and graph a direct variation equation that
relates the variables.
38. PHYSICAL SCIENCE The weight W of an object
2
is 9.8 m/s times the mass of the object m.
ANSWER: W = 9.8 m
, find x when y = 16.
ANSWER: 29. FINANCIAL LITERACY Depreciation is the
decline in a car’s value over the course of time. The
table below shows the values of a car with an
average depreciation.
a. Write an equation that relates the age x of the car
to the value y that it lost after each year.
b. Find the age of the car if the value is $300
39. MUSIC Music downloads are $0.99 per song. The
total cost of d songs is T.
ANSWER: T = 0.99d
ANSWER: a. y = 1800x
b. 7 yr 6 mo
Suppose y varies directly as x. Write a direct
variation equation that relates x and y. Then
solve.
, find x when y = 25.
31. If y = 15 when
ANSWER: y = 20x;
eSolutions
Manual - Powered by Cognero
33. If y = –6 when x = 1.6, find y when x = 8.
40. GEOMETRY The circumference of a circle C is
approximately 3.14 times the diameter d.
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ANSWER: C = 3.14d
3-4 Direct Variation
40. GEOMETRY The circumference of a circle C is
approximately 3.14 times the diameter d.
ANSWER: C = 3.14d
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