2.3 Direct Variation
A linear function defined by the equation of the form y = kx, where k = 0 represents a direct variation. The slope k is constant and the y­intercept is (0, 0).
k is called the constant of variation
Determine if the table represents a direct variation. If so, find the constant of variation and write the equation.
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Determine if the equation represents a direct variation. If so, find the constant of variation.
a) 3y = 7x + 7
b) 5x = ­2y
c) The circumference of a circle varies directly with the diameter. The formula C = d relates the circumference to the diameter.
1) What is the constant of variation?
2) Find the diameter if the circumference is
105 cm.
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Suppose y varies directly as x, and x = 27 when y = ­51. Find x when y = ­17.
2.3 pp. 74, 75 #2­22 (E), 34, 38, 52 and quiz review p.838 #3, 7, 10, 17, 25, 31
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