1. 5-5 Direct Variation

2. Ex. 1 Is Direct Variation?

3. Your Practice Is 3y + 4x = 8 an example of direct variation? No, does not equal zero.

4. Ex. 2 Writing an Equation

5. Your Practice

6. Ex. 3 Story Problems Your distance from lightning varies directly with the time it takes you to hear thunder. If you hear thunder 10 seconds after you see lightning, you are about 2 miles from the lightning. Write an equation for the relationship between time and distance. Whatever comes before “varies directly” is y – y = 2 Whatever comes after “varies directly” is x – x = 10 Put into y = kx to find k and write equation – 2 = k(10) – 2 = 10k – 10 10 – 1 = k –5–5 So y = 1/5k

7. Your practice

8. Ex. 4 Direct Variation and Tables xyy/xdecimal -32.252.25/3-0.75 1 -.75/1-0.75 4-3-3/4-0.75 6-4.5-4.5/6-0.75

9. Your Practice Is the table show direct variation and if so, what is the equation? Check y/x and decimal to be the same k = 1.8 y = 1.8x xy 35.4 712.6 1221.6 y/xdecimal 5.4/31.8 12.6/71.8 21.6/121.8