Download Lesson 3-4 Direct Variation with answers.notebook

Lesson 3­4 Direct Variation with answers.notebook
Questions/Main Ideas
October 21, 2014
Lesson 3­4 Direct Variation
direct variation ­ described by an equation y = kx where k ≠0.
there is a constant rate of change, k, also known as the constant of variation or constant of proportionality
Example 1
Name the constant of variation for each equation. Then find the slope of the line that passes through each pair of points.
a.
b.
Questions/Main Ideas
Notice ­ the graph of y = kx always passes through the origin
the x­ and y­intercepts are zero
Example 2
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Graph y = x
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Lesson 3­4 Direct Variation with answers.notebook
October 21, 2014
Questions/Main Ideas
Questions/Main Ideas
Example 3
Suppose y varies directly as x, and y = 9 when x = −3.
a. Write a direct variation equation that relates x and y.
b. Use the direct variation equation to find x when y = 15.
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Lesson 3­4 Direct Variation with answers.notebook
Questions/Main Ideas
October 21, 2014
Common direct variation problem:
d = rt
Distance d varies directly as time t, and the rate r is the constant of variation.
Example 4
The Ramirez family is driving cross­country on vacation. They drive 330 miles in 5.5 hours.
a. Write a direct variation equation to find the distance d driven in time t.
b. Graph the equation.
Questions/Main Ideas
c. Estimate how many hours it would take to drive 500 miles.
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Lesson 3­4 Direct Variation with answers.notebook
October 21, 2014
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Lesson 3­4 Direct Variation with answers.notebook
October 21, 2014
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Lesson 3­4 Direct Variation with answers.notebook
October 21, 2014
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