2. Language Goal  Students will be able to verbally express direct variation. Math Goal  Students will be able to identify, write, and graph direct variation. Essential Questions  Why is direct variation a special type of linear relationship?

6.  Direct Variation  Constant of Variation A linear relationship that can be written in the form y = kx. A nonzero constant (k) in a direct variation.

7.  Tell whether each equation represents a direct variation. (y = kx)  If so identify the constant of variation. (k)  You may have to solve for y first! A. y = 4x B. -3x + 5y = 0 C. 2x + y = 10

8.  Tell whether each equation represents a direct variation. (y = kx)  If so identify the constant of variation. (k)  You may have to solve for y first! D. 3y = 4x + 1 E. 3x = -4y F. y + 3x = 0

9. x 135 y 61830

11. x 248 y -204

12. x -313 y 036

13. x 2.557.5 y -10-20-30

14.  Again two methods.  Method 1: Find the value of k and then write the equation.  Method 2: Use a proportion.

15.  The value of y varies directly with x, and y = 6 when x = 12. Find y when x = 27. Method 1: Method 2:

16.  The value of y varies directly with x, and y = 4.5 when x = 0.5. Find y when x = 10. Method 1: Method 2:

17.  The value of y varies directly with x, and y = 3 when x = 9. Find y when x = 21.

18.  Not doing example 4.

19.  Lets Review!

20.  Identify whether the graph is a function.  If yes, is it linear? Function? Linear? Function? Linear? Function? Linear?

21.  Does the set of ordered pairs satisfy a linear function? Explain. {(1,.5), (4, 1), (7, 1.5), (10, 2)}

22.  Use intercepts to graph a line of the equation -6x – 3y = 24  Describe the correlation.

23.  Find the x and y intercept from the graph below.

24.  Find the slope of the following graph. Rise: _______Run:_______ Slope: ________

25.  Draw a graph that has a positivie, negative, zero, or no correlation.

26.  Find the slope between points (-4, 9) and (6, -5)

27.  Find the slope of the linear function. xy -2-4 0-3 2-2 4 60

28.  Find the slope of the line 6x + 8y =48

29.  Tell whether the function is a direct variation or not. Explain. A. y = 8xB. y = 2x + 1

30.  The value of y varies directly with x. And y = 21 and x = 7. Find y when x = 4.

31.  Come see me before school if you have any questions when studying.  Quiz is tomorrow!