Download 5-5 Direct Variation 5-5 Direct Variation 5-5 Direct Variation 5

5-5
Direct Variation
5-5
Direct Variation
The Plan For Today
• Correct 5-3
• WAYD/Self-Eval/Conferences
• Questions on 5-4
• Daily L to J
• Lesson 5-5 (p.326-328)
A direct variation is a special type of linear
relationship that can be written in the form
y = kx, where k is a nonzero constant called
the constant of variation.
Identify, write, and graph direct
variation.
• Assignment 5-5
Quiz: 5-1 to 5-5 – Tues. 11/11
HWQ #11 – Thurs. 11/13
Holt Algebra 1
5-5
Holt Algebra 1
Direct Variation
5-5
Direct Variation
Example 1A: Identifying Direct Variations from
Equations
Example 1B: Identifying Direct Variations from
Equations
Tell whether the equation represents a direct
variation. If so, identify the constant of variation.
Tell whether the equation represents a direct
variation. If so, identify the constant of variation.
y = 3x
3x + y = 8
Holt Algebra 1
5-5
Holt Algebra 1
Direct Variation
What happens if you solve y = kx for k?
y = kx
Divide both sides by x (x ≠ 0).
5-5
Direct Variation
Example 2A: Identifying Direct Variations from
Ordered Pairs
Tell whether the relationship
is a direct variation. Explain.
So, in a direct variation, the ratio is equal to
the constant of variation. Another way to identify
a direct variation is to check whether
is the
same for each ordered pair (except where x = 0).
Holt Algebra 1
Holt Algebra 1
1
5-5
Direct Variation
Example 2B: Identifying Direct Variations from
Ordered Pairs
Tell whether the relationship
is a direct variation. Explain.
Holt Algebra 1
5-5
5-5
Direct Variation
Example 3: Writing and Solving Direct Variation
Equations
The value of y varies directly with x, and y = 3,
when x = 9. Find y when x = 21.
Holt Algebra 1
Direct Variation
5-5
Direct Variation
Example 4: Graphing Direct Variations
A group of people are tubing down a river at an
average speed of 2 mi/h. Write a direct
variation equation that gives the number of
miles y that the people will float in x hours.
Then graph.
Holt Algebra 1
5-5
Today’s Assignment
5-5
p. 329-331
10-18 even, 20-24, 36,
41-43, 47-55 odd
Holt Algebra 1
Direct Variation
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Holt Algebra 1
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