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Section 2.2 – DIRECT Variation. Some quantities are in a relationship where the ratio of corresponding values is constant. You can write a formula for a direct variation function as y = kx or y/x = k, where k CAN NOT equal 0, x represents input values, and y represents output values
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Section 2.2 – DIRECT Variation Some quantities are in a relationship where the ratio of corresponding values is constant. You can write a formula for a direct variation function as y = kx or y/x = k, where k CAN NOT equal 0, x represents input values, and y represents output values The formula y/x = k says that, except (0,0), the ratio of all output-input pairs equals the constant k, the constant of variation.
Section 2.2 – DIRECT Variation Problem 1: For each function, determine whether y varies directly with x. If so, what is the constant of variation and the function rule?
Section 2.2 – DIRECT Variation Problem 1: For each function, determine whether y varies directly with x. If so, what is the constant of variation and the function rule?
Section 2.2 – DIRECT Variation Problem 2: For each function, determine whether y varies directly with x. If so, what is the constant of variation? 3y = 7x 7y = 14x + 7 5x + 3y = 0 y = x/9
Section 2.2 – DIRECT Variation In direct variation, y/x is the same for all pairs of data where x = 0. So is true for the ordered pairs (x1 ,y2) and (x2 ,y2) where neither x1 nor x2 is zero.
Section 2.2 – DIRECT Variation Problem 3: Suppose y varies directly with x, and y = 9 when x = -15. What is y when x = 21?
Section 2.2 – DIRECT Variation Problem 3: Suppose y varies directly with x, and y = 15 when x = 3. What is y when x = 12?
Section 2.2 – DIRECT Variation Problem 4: A salesperson’s commission varies directly with sales. For $1000 in sales, the commission is $85. What is the commission for $2300 in sales?
Section 2.2 – DIRECT Variation Problem 4: The number of Calories varies directly with the mass of cheese. If 50 grams of cheese contain 200 calories, how many calories are in 70 grams of cheese?
Section 2.2 – DIRECT Variation Problem 4: If y2 varies directly with x2, does that mean that y must vary directly with x? Explain!
Section 2.2 – DIRECT Variation Problem 5: What is the graph of each direct variation equation? a. y = -2x y = 3x