1. Special Linear Case: Proportional Situations 2.14

2. I need potatoes! I need a whole lot of potatoes to make some delicious potato soup for a huge party Yummy!

3. Two Options Costco: - Pay $20 membership fee - $2 per pound of potatoes Lucky’s: - $4 per pound of potatoes

4. Let x = number of pounds Let y = total cost Costco: - Pay $20 membership fee - $2 per pound of potatoes y = 2x + 20 Lucky’s: - $4 per pound of potatoes y = 4x What’s different about the equation for Lucky’s?

5. Costco: y = 2x + 20 Lucky’s: y = 4x What’s different about the graph for Lucky’s?

6. What’s true about all of these graphs? What’s true about all of these equations?

7. Notes

8. Vocabulary Proportional linear equations = have an initial value (y-intercept, b) of 0 Direct Variation = another name for a proportional relationship “y varies directly as x” means the graph is proportional Constant of Variation = the slope (m) of a proportional linear equation

9. Team Practice Using any method your team comes up with, determine if the points in the table represent a proportional relationship or not. x23410 y8121640

10. Practice: Proportional or not? x3456 y57911 x46810 y691215 x12151824 y8101216