1. Proportional Relationships and Graphs & Constant of Proportionality
You will need
GRAPH PAPER
for today’s lesson
Proportional Relationships and Graphs & Constant of Proportionality
Section 2-2 & 2-3

2. Complete the Launch Activity for Section 2-2

3. Watch the Key Concept video

4. When graphed, what does a proportional relationship look like?
When graphed, a proportional relationship is a straight line that travels through the origin.
The origin is the starting point. On a number line it is 0. On a two-dimensional graph it is where the X axis and Y axis cross, marked (0, 0) on the graph here:

5. Sketch these examples onto your graph paper:

7. Equation of a line:

9. When written as an equation, a proportional relationship is written as y = kx, where k is the constant of proportionality.

10. Y-Intercept must be 0 for the line to pass through the origin and show a proportional relationship.
Which of the following equations represent a proportional relationship?
A.) y = x B.) y = x² C.) y = 5x D.) y = -4x E.) y = x + 3 F.) y = 6x -2 G.) y = 0.4x H.) y = ⅓x

12. Complete the Launch Activity for Section 2-3

13. In y = x2 x is an Independent Variable y is the Dependent Variable
Independent Variable: those variables whose values determine the value of other variables (input value).
Dependent Variable - those variables whose values are determined with the help of the independent variable (output value).
In y = x2 x is an Independent Variable y is the Dependent Variable

14. Which is your dependent? Which is your independent?
a.) How much money you make and how many hours you work for.
b.) The amount of water you feed a plant and how tall it grows.
c.) The cost of your cell phone bill and the number of minutes you talk.

15. Constant of Proportionality = Unit Rate