Question

I need help about math set

Answer 1

@mathmate

Answer 2

...yes?

Answer 3

If A = {a, b, {a, c}, ∅} and B = {a, {a}, d, e},
Then:
A - ∅ ?

Answer 4

@zepdrix @563blackghost @inkyvoyd

Answer 5

Hint:
Link will give answer AND explains why. Be sure to read the proof!
https://proofwiki.org/wiki/Set_Difference_with_Empty_Set_is_Self

Answer 6

which one is it?

Answer 7

∅ is also part of A. That's make me confused :s

Answer 8

Hi @Loser66
Would you help me?

Answer 9

if your family has you, your mom, your dad and your sister
what is the family member without you?

Answer 10

So, it's
a, b, {a, c} ?

Answer 11

Dat sit

Answer 12

Next question,
A - {∅}

Answer 13

Hi @jango_IN_DTOWN
Would you help me?

Answer 14

what is the question?

Answer 15

If A = {a, b, {a, c}, ∅} and B = {a, {a}, d, e},
Then:
a. A - ∅ ?
b. A - {∅} ?

Answer 16

A-∅ =A
A-{∅ }={a, b, {a, c}}
In the first case ∅ is the empty set
In the second case {∅} this set is deducted from A

Answer 17

Thx!
I need more help

Answer 18

/post in a new thread .

Answer 19

Ok :(

Answer 20

but it's still same question

Answer 21

okay

Answer 22

c. { {a, c} } - A
It's ∅ right?

Answer 23

correct

Answer 24

{a} - {A}
I don't understand this one

Answer 25

/i guess it will be ∅ again

Answer 26

Next question,
P (A - B)

Answer 27

We supposed to count elements?

Answer 28

What does P(A) stands for here?

Answer 29

That's it, I don't understand

Answer 30

Generally P stands for probability,

Answer 31

But not here

Answer 32

maybe power set

Answer 33

Oh yeah, but it has a different symbol. :) like P, but not P. ok..

Answer 34

So tell me what is A-B here?

Answer 35

Here is the example
If A = {1, 2}, Then P(A) = {∅, {1}, {2}, {1, 2}}

Answer 36

That's it, I guess
A-B = {a, b, {a, c}, ∅} - {a, {a}, d, e}
A-B = {b, {c}, ∅}
Pls check it again, coz I really don't understand with this

Answer 37

A-B contains those elements of A which are not in B.. TRy once again finding A-B

Answer 38

Hmmm,, what is it?

Answer 39

Do one by one, first take the element a of A. Is it in B? The answer is yes. So we cannot include a in A-B.. Do similarly and give me the answer

Answer 40

Well let me write it, you check if I am correct
A-B={ b, {a, c}, ∅}

Answer 41

Now take the power set. It will give the answer

Answer 42

Power set is the set of all possible subsets which can be formed using this set A-B

Answer 43

It will contain 2^3=8 elements

Answer 44

P(A-B)={b,{a,c},∅,{b,{a,c}},{b,∅},{{a,c},∅},{ b, {a, c}, ∅}}

Answer 45

see we got 8 elements Bingoooo

Answer 46

@Kevin

Answer 47

hmm... but how do you not eliminate (a) in A?
A-B = {a, b, {a, c}, ∅} - {a, {a}, d, e}
Sorry, I still understand this part

Answer 48

a and {a} are not the same

Answer 49

what is the difference?

Answer 50

a is an element. and {a} is a set

Answer 51

so, is there any set of a in A?

Answer 52

I'm thinking to eliminate a from {a, c} in A. But that's not right, right?

Answer 53

While evaluating A-B, you need to look at those elements of A, which are not in B . Those will give the answer.
No {a} and {a,c} are again different sets. You cannot cancel.

Answer 54

I see, thx.
I still have same question

Answer 55

Which question? . :)

Answer 56

B²

Answer 57

B*B? Its the cartesian product

Answer 58

Should I write the element twice?

Answer 59

still have no clue

Answer 60

No B*B ={(b,b) b belongs to B}

Answer 61

Let me give you an example
Let B={1,2}
Then B*B={(1,1),(1,2),(2,1),(2,2)}

Answer 62

I see now :)

Answer 63

Wait, should it be like power set?

Answer 64

No. Power set will contain all subsets.. Let me tell you how to compute B*B.

Answer 65

Like this?

Answer 66

. :)correct/