Question

what does this mean---> A ∩ B

Answer 1

The intersection of set A and set B

Answer 2

So what would the intersection be for this? A = {3, 6, 9, 12} and B = {2, 4, 6, 8, 10, 12}.

Answer 3

The intersection of sets is the set of elements that appear in both sets

for example:

if \(X=\{a,b,c\}\) and \(Y=\{c,d,e\}\)

The intersection of \(X\) and \(Y\)

is \[X∩Y=\{a,b,c\}∩\{c,d,e\}=\{c\}\]

Answer 4

so would it be 6?

Answer 5

yeah 6 is in both sets so it will be in the intersection, but there is another element as well

Answer 6

like, another number?

Answer 7

yes there are two elements in the intersection of this A and B

Answer 8

12

Answer 9

good so you have found
\[A\cap B=\{3,6,9,12\}\cap\{2,4,6,8,10,12\}=\{6,12\}\]

Answer 10

whts it mean if the thing between A and B is like a U?

Answer 11

\(\cup\) is the symbol for union.
The union of sets is the set that contains all the elements in the first set and the second set
for example:

if \(X=\{a,b,c\}\) and \(Y=\{c,d,e\}\)

the Union of \(X\) and \(Y\)

is \(X∪Y=\{a,b,c\}\cup\{c,d,e\}=\{a,b,c,d,e\}\)

(notice that the union has each element appearing only once)

Answer 12

Is it just kind of combining them?

Answer 13

yes, its not very difficult,

Answer 14

Alright, thanks for all the help. It really got me to understand it.

Answer 15

if we have the same A and B as before

A = {3, 6, 9, 12} and B = {2, 4, 6, 8, 10, 12}.



What is the union of A and B ?

\[A\cup B=\{3, 6, 9, 12\}\cup\{2, 4, 6, 8, 10, 12\}=\]

Answer 16

If I'm just combining them then I'd have to say 2,3,4,6,8,9,10,12

Answer 17

Very good! that is right!

Answer 18

So the ∩ means the numbers they have in common and the U means you just mesh them into one?

Answer 19

Yes.

Answer 20

I'd like to note that in set notation, the ordering within a set doesn't matter.

For A∪B you \(\textit {could}\) have wrote {12,8,3,4,6,10,9,2},
and it would also be a correct answer,

(but i personally like to keep the elements in some order, [like you have done])