Set notation

Question 1

A ∩ B

Answer 1

Intersection: in both A and B

Question 2

{ }

Answer 2

Set: a collection of elements
{1, 2, 3, 4}

Question 3

A ∪ B

Answer 3

Union: in A or B (or both)

Question 4

a ∈ A

Answer 4

Element of: a is in A
3 ∈ {1, 2, 3, 4}

Question 5

b ∉ A

Answer 5

Not element of: b is not in A
6 ∉ {1, 2, 3, 4}

Question 6

Ø

Answer 6

Empty set = {}
{1, 2} ∩ {3, 4} = Ø

Question 7

A − B

Answer 7

Difference: in A but not in B
{1, 2, 3, 4} − {3, 4} = {1, 2}

Question 8

U (with double lines)

Answer 8

Universal Set: set of all possible values
(in the area of interest)

Question 9

|A|

Answer 9

Cardinality: the number of elements of set A
|{3, 4}| = 2

Question 10

|

Answer 10

Such that
{ n | n > 0 } = {1, 2, 3,…}

Question 11

:

Answer 11

Such that
{ n : n > 0 } = {1, 2, 3,…}

Question 12

∀

Answer 12

For All
∀x>1, x²>x
For all x greater than 1x-squared is greater than x

Question 13

∃

Answer 13

There Exists
∃ x | x² > x
There exists x such that x-squared is greater than x

Question 14

N ( with doube lines)

Answer 14

Natural Numbers
{1, 2, 3,…} or {0, 1, 2, 3,…}

Question 15

Z (with double lines)

Answer 15

Integers
{…, −3, −2, −1, 0, 1, 2, 3, …}

Question 16

Q (with double lines)

Answer 16

Rational Numbers
Any number which can be written as a fraction

Question 17

A (with double lines)

Answer 17

Algebraic Numbers

Question 18

R (with double lines)

Answer 18

Real Numbers
Any number which doesnt have i

Question 19

I (capital i with double lines)

Answer 19

Imaginary Numbers
3i

Question 20

C (with double lines)

Answer 20

Complex Numbers
2 + 5i

Question 21

2|x

Answer 21

2 divide x is a whole number

Question 22

2∤x

Answer 22

2 divide x is not a whole number

Question 23

What is a set?

Answer 23

A set is a collection of things, usually numbers. We can list each element (or “member”) of a set inside curly brackets like this:
{3,6,91,…}