1. Solve the system of equations: y = -2x + 4 x – 5y = 2
Warm-up Tuesday, 1/15/2013
Solve the system of equations:
y = -2x + 4
x – 5y = 2
3.9.1: Interpreting Parameters

2. Standard(s) and Essential Question:
MCC9‐12.F.LE.5 Interpret the parameters in a linear or exponential function in terms of a context. ★ (Limit exponential functions to those of the form f(x) = bx + k.)
EQ: What are the parameters in an exponential function?
3.9.1: Interpreting Parameters

3. Introduction
In order to fully understand how various functions model real-world contexts, we need to understand how changing parameters will affect the functions. This lesson will explore the effect of changing parameters on linear and exponential functions. We will also interpret the effects of changing these parameters in a context.
3.9.1: Interpreting Parameters

4. Key Concepts
The parameter of a function is a term that determines a specific form of a function but not the nature of the function.
For a linear function written in slope-intercept form, f(x) = mx + b,
the parameters are m and b.
m = slope
b = y-intercept.
Changing either of these parameters will change the function and the graph of the function.
3.9.1: Interpreting Parameters

5. Key Concepts, continued
For an exponential function in the form f(x) = ab x + k,
a = initial amount
b = growth factor, a positive integer not equal to 1
k = the vertical shift or the number of units the graph of the function is moved up or down. It can equal 0,
the parameters are a, b and k.
Changing either of these parameters will change the function and the graph of the function.
3.9.1: Interpreting Parameters

6. Common Errors/Misconceptions
not understanding the difference between variables and parameters in a function
mistaking the slope for the y-intercept or the
y-intercept for the slope
forgetting to identify the vertical shift in the context of an exponential problem
when reading a word problem, not being able to identify the parameters in the context of the problem
3.9.1: Interpreting Parameters

7. Guided Practice Example 1
You visit a pick-your-own apple orchard. There is an entrance fee of $5.00, plus you pay $0.50 for each apple you pick. Write a function to represent this scenario. Complete a table of values to show your total cost if you pick 10, 20, 30, 40, and 50 apples. Graph the line and identify the parameters in this problem. What do the parameters represent in the context of the problem?
3.9.1: Interpreting Parameters

8. Guided Practice: Example 1, continued Write a function.
This scenario is represented by a linear function.
Identify the slope and the y-intercept.
The slope is the $0.50 charged for each apple picked.
The y-intercept is the entrance fee of $5.00.
Substitute the slope and the y-intercept into the linear function f(x) = mx + b, where m is the slope and b is the y-intercept.
The function for this scenario is f(x) = 0.5x + 5.
3.9.1: Interpreting Parameters

9. Guided Practice: Example 1, continued Create a table.
Let x = the number of apples picked and f(x) = the total cost.
Use the values 0, 10, 20, 30, 40, and 50 for x. x
0.5x + 5
f(x)
0.5(0) + 5 10
0.5(10) + 5 20
0.5(20) + 5 15 30
0.5(30) + 5 40
0.5(40) + 5 25 50
0.5(50) + 5
3.9.1: Interpreting Parameters

10. Guided Practice: Example 1, continued Graph the function.
Use the table of values to plot the equation of the line.
3.9.1: Interpreting Parameters

11. ✔ Guided Practice: Example 1, continued Identify the parameters.
The parameters in this problem are the slope and the y- intercept.
In this problem, the y-intercept is the entrance fee, $5.00, and the slope is the cost per apple, $0.50. ✔
3.9.1: Interpreting Parameters

12. Guided Practice Example 2
You deposit $100 into a long-term certificate of deposit (CD) in which your money will double every 7 years. Write a function to show how much money you will have in total in 7, 14, 21, 28, and 35 years. Use the function to create a table, and then graph the function. What do the parameters represent in the context of this problem?
3.9.1: Interpreting Parameters

13. Guided Practice: Example 2, continued Write a function.
This scenario is represented by an exponential function.
The initial deposit is $100.
Your money doubles every 7 years, so the growth factor is 2.
The time period is 7 years.
Substitute these values into the exponential function.
The function for this scenario is
3.9.1: Interpreting Parameters

14. Guided Practice: Example 2, continued Create a table.
Let x = the number of years and f(x) = the amount of money in dollars.
Use the values 7, 14, 21, 28, and 35 for x.
3.9.1: Interpreting Parameters

15. Guided Practice: Example 2, continued
f(x) 7
200 14
400 21
800 28
1600 35
3200
3.9.1: Interpreting Parameters

16. Guided Practice: Example 2, continued Graph the function.
Use the table of values to plot the function.
3.9.1: Interpreting Parameters

17. ✔ Guided Practice: Example 2, continued Identify the parameters.
The parameters in this problem are the starting amount of $100 and the base of 2. ✔
3.9.1: Interpreting Parameters

18. Closing:
Four Two One
Students will individually generate four (4) words that capture the most important aspects of the learning task
Then, share with learning partners their four words and compile a list of the words they have in common. From this list, determine two words that they agree capture the most important aspects.
Determine the 1 word or big idea that best represents the most important learning of the experience.
Share the various lists generated by their group in order for the whole class to make as many learning connections as possible.