Tell whether each equation is function. Write Function or Not a Function. 1. y=3x 2. y=-2x y=20/x Function Not a Function

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Objective: To learn -the concept of direct variation and its affect on a situation

 Direct Variation—a function of the form __________________, where k ≠ 0.  k is the “______________________________” ◦ it is the coefficient of x ◦ The variables y and x are said to “________________” ◦ When graphed, the y-intercept (b) is _____________. y=kx Constant of Variation vary directly zero

Example 1:Example 2: y = 3x y = -x Constant of Variation: Graph: 3

Tell whether the equation is direct variation. If it is, find the constant of variation. 1) y = 2x 2) 2x + 5y = 1 3) -12x = 6y 4) y + 8 = -x 5) 5x – 6y = 0 6) -x = 10y Direct Variation, k=2 NOT a Direct Variation Direct Variation, k=-2 NOT a Direct Variation Direct Variation, k=5/6 Direct Variation, k=-1/10

Write an equation of direct variation that includes the given point: 1) (1, 5) 2) (-8, 10) 3) (-6, 1) 4) (3, -4) y=5x y=(-5/4)x or y=-1.25x y=(-1/6)x y=(-4/3)x

Assume that y varies directly with x: 5) If y = 28 when x = 7, find x when y = 52 6) If y = 2.5 when x = 0.5, find x when y = 20 7) If y = 4 when x = 12, find y when x = -24 8) If y = 2 2/3 when x = ¼, find y when x= 1 1/8

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CW: Demonstration HW: Direct Variation Applications WS #2-6, 8