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Homework Answers

1. {3}2. {1, 3}5. {3, 4, 6}6. {}10. {2, 3, 4}11. {1, 3, 4}14. {5}

16. {3, 4}22. {}23. {8}24. C = {8}28*. D = {6, 8}32. B = {2, 4, 8}

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Lesson 9

Sets and their Union

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Review on Sets

• A set is a collection of elements.• A finite set is a set whose number of elements can be

counted.• An infinite set is a set whose number of elements

CANNOT be counted.• The empty set (or null set) is a set that has NO

ELEMENTS { } Or { }• A subset is a smaller set from a larger set. Symbol for

subset is • The complement of a set is the set of all the elements that

belong to a LARGER set but DO NOT belong in a given subset.

• The intersection of sets is the set of all the elements that belong to both sets. Symbol for intersection is

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Union of Sets

• The union of sets is a set that contains all possible elements from both sets without duplicates.– Symbol for union is

– Ex: A B

• Ex: A = {A, B, C, D, E}

B = {A, E, I, O, U}

List the elements of the resulting set

A B

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Practice

• Let A = {1, 2, 3, 4, 5}

• Let B = {1, 3, 5, 7, 9}

• Let C = {2, 4, 6, 8, 10}

Solve the following:

1. A B 2. A B 3. B C 4. C A

5. C 6. B C 7. C C

8. (A B) C