1. 1-4: Patterns and Functions
Essential Question:

2. 1-4: Patterns and Functions
A function is a relationship that assigns exactly one output value for each input value. For each input value, there is only one corresponding output.
A function rule, such as C = p p, is an equation that defines a functional relationship.

3. 1-4: Patterns and Functions
Example 1: Writing a Function Rule
The relationship between the number of loads of laundry and cost is given below. Use the table to write a function rule.
Determine variable names to use
Let n = number of loads Let c = cost
Determine the difference between successive entries.
$ $2.75 = $2.75 $ $5.50 = $11.00 – $8.25 = 2.75
Work backwards to determine if there would have been any cost with 0 loads.
Nope
c = 2.75 • n

4. 1-4: Patterns and Functions
Your Turn: Writing a Function Rule
The relationship between the number of hours and the total miles driven is given below. Use the table to write a function rule.
m = 60 • h

5. 1-4: Patterns and Functions
Example 2: Writing a Function Rule (with starting point)
The relationship between the number of houses built and number of toothpicks used.
Determine variable names to use
Let h = number of houses
Let t = number of toothpicks
Determine the difference between successive entries.
11 – 6 = 5 16 – 11 = 5 21 – 16 = 5
Work backwards to determine if there would have been any cost with 0 houses.
6 – 5 = 1
c = 5 • n + 1

6. 1-4: Patterns and Functions
Your Turn: Writing a Function Rule (with a starting point)
The relationship between an input (x) and output (y) is given below. Determine the function for the data in the table.
y = 3x + 2

7. 1-4: Patterns and Functions
The relationship between the number of houses built and number of toothpicks used.
In this example, the number of toothpicks t depends on the number of houses h to be built.
This makes t the dependent variable, and h the independent variable.
In most real-world scenarios, the independent variable is the one you can control.

8. 1-4: Patterns and Functions
Example 3
The cost of a memory stick is shown in the table below. Determine the dependent and independent variables.
Because the cost DEPENDS on the amount of memory you wish to purchase, the cost is the dependent variable
Because you control how much memory you wish to buy, memory is the INDEPENDENT variable.

9. 1-4: Patterns and Functions
Your Turn
Determine the independent and dependent variable in the scenario below.
The cooking time for an unstuffed turkey is about 20 minutes per pound.
Dependent variable:
Independent variable:
The cooking time
The number of pounds to cook

10. 1-4: Patterns and Functions
The possible values for input (or independent variable) of a function are the domain of the function. The possible values of the output (dependent variable) are the range of the function.
Example 4: Reasonable domain and range
Maria earns $7 an hour for babysitting after school and on Saturday. She works no more than 16 hours a week.
Identify the independent and dependent quantities
She controls the number of hours she works, so that is the independent variable.
The amount she earns is the dependent variable (her pay DEPENDS on the amount of hours she works)
Find a reasonable domain and range for this situation
She works no more than 16 hours a week, so a reasonable domain is anything from 0 to 16 hours.
A reasonable range is anything from $0 to $112 (7 • 16)

11. 1-4: Patterns and Functions
Your Turn
Charlie downloads songs for $0.75 each. He has between $3.00 and $6.00 to spend on songs.
Identify the independent and dependent variables.
Independent variable: The amount of money he decides to spend
Dependent variable: How many songs he downloads
Find a reasonable domain and range.
Domain: Anything from $3 to $6
Range: Anything from 4 to 8 songs (3/0.75 and 6/0.75)

12. 1-4: Patterns and Functions
Assignment
Practice Worksheet 1-4
All problems
Tomorrow
Quiz on Sections 1-1 through 1-3