Corrections 143-146

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• 1) a) $1.5/year the value increases by $1.5 per year

• B) $0 /year the value remained constant• C) $- 6/year the value decreased by $6 per

year

• 2) a) y = 15• B) horizontal line through y = 15• C) constant or zero variation

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• 3)• A) y = 30x• C) direct variation

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• 4)• A) y = 10x + 15• c) Partial variation

• 5) a) y = 1200 / x

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• 6. a) $15• B) 120• C) y = 15x – 120• D) 1. less than 8 2. More than 8

• 7) a) 15 000 Litres (find a and b values, write rule, then set x equal to7 hours) y = -5000 x + 50 000

• B) 10 hours (replace y with 0)

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• 8 a) independent: time• Dependent: volume of water in the tank• B) y = -5t + 80• C) 1. replace y with 0 and solve for t 16

hours• 2. the graph hits the x axis (where y = 0) at t =

16 hours

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• 9)• A) A: y = 300 B: y = 10x C: y = 5x + 100• B) A: zero B: direct C: Partial• D) if the employee sells less than 30 items• E) if the employee sells more than 30 items• F) c is never the best option (it never has the

greatest y value)

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• 10) x = # of videos y = cost • A: y = 2.5x + 10• B: y = 3x• Use comparison to see how many videos it would

take before the cost is the same• 3x = 2.5x + 10 x = 20 videos• If you rent more than 20 videos per year, option

A is better. Less than 20, option B is better