1. Relations and Functions
Section 1-6
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1-6 Relations and Functions

2. 1-6 Relations and Functions
Review
A relation between two variables x and y is a set of ordered pairs
An ordered pair consist of a x and y-coordinate
A relation may be viewed as ordered pairs, mapping design, table, equation, or written in sentences
x-values are inputs, domain, independent variable
y-values are outputs, range, dependent variable
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3. 1-6 Relations and Functions
Example 1
What is the domain?
{0, 1, 2, 3, 4, 5}
What is the range?
{-5, -4, -3, -2, -1, 0}
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4. 1-6 Relations and Functions
Example 2 4 –5 9 –1
Input –2 7
Output
What is the domain?
{4, -5, 0, 9, -1}
What is the range?
{-2, 7}
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5. Is a relation a function?
What is a function?
According to the textbook, “a function is…a relation in which every input is paired with exactly one output”
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6. Is a relation a function?
Focus on the x-coordinates, when given a relation
If the set of ordered pairs have different x-coordinates,
it IS A function
If the set of ordered pairs have same x-coordinates,
it is NOT a function
Y-coordinates have no bearing in determining functions
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7. 1-6 Relations and Functions
Example 3
:00
Is this a function?
Hint: Look only at the x-coordinates
YES
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8. 1-6 Relations and Functions
:40
Example 4
Is this a function?
Hint: Look only at the x-coordinates NO
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9. 1-6 Relations and Functions
:40
Example 5
Which mapping represents a function?
Choice One Choice Two 3 1 –1 2 2 –1 3 –2
Choice 1
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10. 1-6 Relations and Functions
Example 6
Which mapping represents a function?
A B. B
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11. 1-6 Relations and Functions
Example 7
Which situation represents a function?
a. The items in a store to their prices on a certain date
b. Types of fruits to their colors
A fruit, such as an apple, from the domain would be associated with more than one color, such as red and green. The relation from types of fruits to their colors is not a function.
There is only one price for each different item on a certain date. The relation from items to price makes it a function.
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1-6 Relations and Functions

12. 1-6 Relations and Functions
Vertical Line Test
Vertical Line Test: a relation is a function if a vertical line drawn through its graph, passes through only one point. AKA: “The Pencil Test” Take a pencil and move it from left to right (–x to x); if it crosses more than one point, it is not a function
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1-6 Relations and Functions

13. 1-6 Relations and Functions
Vertical Line Test
Would this graph be a function?
YES
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14. 1-6 Relations and Functions
Vertical Line Test
Would this graph be a function? NO
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15. 1-6 Relations and Functions
Is the following function discrete or continuous? What is the Domain? What is the Range?
Discrete
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16. 1-6 Relations and Functions
Is the following function discrete or continuous? What is the Domain? What is the Range?
continuous
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17. 1-6 Relations and Functions
Is the following function discrete or continuous? What is the Domain? What is the Range?
continuous
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18. 1-6 Relations and Functions
Is the following function discrete or continuous? What is the Domain? What is the Range?
discrete
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19. 1-6 Relations and Functions
Domain and Range in Real Life
The number of shoes in x pairs of shoes can be expressed by the equation y = 2x.
What subset of the real numbers makes sense for the domain?
Whole numbers
What would make sense for the range of the function?
Zero and the even numbers
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20. 1-6 Relations and Functions
Domain and Range in Real Life
The number of shoes in x pairs of shoes can be expressed by the equation y = 2x.
What is the independent variable?
The # of pairs of shoes.
What is the dependent variable?
The total # of shoes.
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21. 1-6 Relations and Functions
Domain and Range in Real Life
Mr. Landry is driving to his hometown. It takes four hours to get there. The distance he travels at any time, t, is represented by the function d = 55t (his average speed is 55mph.
Write an inequality that represents the domain in real life.
Write an inequality that represents the range in real life.
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22. 1-6 Relations and Functions
Domain and Range in Real Life
Mr. Landry is driving to his hometown. It takes four hours to get there. The distance he travels at any time, t, is represented by the function d = 55t (his average speed is 55mph.
What is the independent variable?
The time that he drives.
What is the dependent variable?
The total distance traveled.
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23. 1-6 Relations and Functions
Domain and Range in Real Life
Johnny bought at most 10 tickets to a concert for him and his friends. The cost of each ticket was $12.50.
Complete the table below to list the possible domain and range. 1 2 3
12.50
25.00
37.50 4 5 6 7 8 9 10 50
62.50 75
87.50
100
112.50
125
What is the independent variable?
The number of tickets bought.
What is the dependent variable?
The total cost of the tickets.
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24. 1-6 Relations and Functions
Domain and Range in Real Life
Pete’s Pizza Parlor charges $5 for a large pizza with no toppings. They charge an additional $1.50 for each of their 5 specialty toppings (tax is included in the price).
Jorge went to pick up his order. They said his total bill was $9.50. Could this be correct? Why or why not?
Yes
One pizza with 3 toppings cost $9.50
Susan went to pick up her order. They said she owed $ Could this be correct? Why or why not? No
One pizza with 4 toppings cost $11
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25. 1-6 Relations and Functions
Domain and Range in Real Life
Pete’s Pizza Parlor charges $5 for a large pizza with no toppings. They charge an additional $1.50 for each of their 5 specialty toppings (tax is included in the price).
What is the independent variable?
The number of toppings
What is the dependent variable?
The cost of the pizza
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26. 1-6 Relations and Functions
Function Notation
f(x) means function of x and is read “f of x.”
f(x) = 2x + 1 is written in function notation.
The notation f(1) means to replace x with 1 resulting in the function value.
f(1) = 2x + 1
f(1) = 2(1) + 1
f(1) = 3
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27. 1-6 Relations and Functions
Function Notation
Given g(x) = x2 – 3, find g(-2) .
g(-2) = x2 – 3
g(-2) = (-2)2 – 3
g(-2) = 1
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28. 1-6 Relations and Functions
Function Notation
Given f(x) = , the following.
a. f(3)
b. 3f(x)
c. f(3x)
f(3) = 2x2 – 3x
f(3) = 2(3)2 – 3(3)
f(3) = 2(9) - 9
f(3) = 9
3f(x) = 3(2x2 – 3x)
3f(x) = 6x2 – 9x
f(3x) = 2x2 – 3x
f(3x) = 2(3x)2 – 3(3x)
f(3x) = 2(9x2) – 3(3x)
f(3x) = 18x2 – 9x
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29. 1-6 Relations and Functions
For each function, evaluate f(0), f(1.5), f(-4),
f(0) =
f(1.5) =
f(-4) = 3 4 4
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30. 1-6 Relations and Functions
For each function, evaluate f(0), f(1.5), f(-4),
f(0) =
f(1.5) =
f(-4) = 1 3 1
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31. 1-6 Relations and Functions
For each function, evaluate f(0), f(1.5), f(-4),
f(0) =
f(1.5) =
f(-4) = -5 1 1
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