1. Direct vs. Inverse Variation

2. Direct Variation As one variable increases, the other must also increase ( up, up) OR As one variable decreases, the other variable must also decrease. (down, down)

3. Real life? With a shoulder partner take a few minutes to brainstorm real life examples of direct variation. Write them down. Food intake/weight Exercise/weight loss Study time/ grades

4. Direct Variation y = kx k is the constant of variation the graph must go through the origin (0,0) and must be linear!!

5. Direct Variation Ex 1)If y varies directly as x and y = 12 when x = 3, find y when x = 10. 2 ways to solve….

6. What did we do? Use y=kx FIRST: Find your data points! (x,y) NEXT: substitute your values correctly LAST: cross multiply to solve for missing variable. FIRST: Find your data points! (x,y) NEXT: Solve for k & write your equation LAST: use your “unknown” data point to solve for the missing variable. EITHER ONE WILL WORK!! ITS YOUR CHOICE!

7. Direct Variation Application Ex 2) In scuba diving the time (t) it takes a diver to ascend safely to the surface varies directly with the depth (d) of the dive. It takes a minimum of 3 minutes from a safe ascent from 12 feet. Write an equation that relates depth (d) and time (t). Then determine the minimum time for a safe ascent from 1000 feet?

8. Inverse Variation As one variable increases, the other decreases. (or vice versa)

9. Inverse Variation This is a NON-LINEAR function (it doesn’t look like y=mx+b) It doesn’t even get close to (0, 0) k is still the constant of variation

10. Real life? With a shoulder partner take a few minutes to brainstorm real life examples of inverse variation. Write them down. Driving speed and time Driving speed and gallons of gas in tank

11. Inverse Variation Ex 3) Find y when x = 15, if y varies inversely as x and when y = 12, x = 10. 2 ways to solve…

12. What did we do? FIRST: Find your data points! (x,y) NEXT: substitute your values correctly LAST: use algebra to solve for missing variable. FIRST: Find your data points! (x,y) NEXT: Find the missing constant, k,by using the full set of data given LAST: Using the formula and constant, k, find the missing value in the problem EITHER ONE WILL WORK!! ITS YOUR CHOICE!

13. Inverse Variation Application Ex 4)The intensity of a light “I” received from a source varies inversely with the distance “d” from the source. If the light intensity is 10 ft-candles at 21 feet, what is the light intensity at 12 feet? Write your equation first.

14. REFLECTION With a shoulder partner, use the “LEFT” side in your notebook and create a Double Bubble Map to compare/contrast Inverse and Direct Variation Hmm…what did I learn?

15. Direct vs. Inverse Variation