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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 What did you like? What didn’t you like? What did you learn? What isn’t quite clear? ______ is awesome! Please stop _________. Anything else… Holt Algebra 1 2