Can someone clear this up please? (should be pretty simple) Watch

monk1324
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#1
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So I'm not sure about the difference between b) and c) in this question. c) is surely true because the set that contains only one element (which is 7) is obviously a subset of A.
I think b) should be true as well. 7 is an element of a subset of A so 7 must be an element of A as well, right? Would a curly bracket not make any difference in this case?

Also (only answer this one if you can be bothered), for a) as you can see the question asks to justify that 0 is an element of A but it obviously is. It's just there, how would I justify it?
Thanks
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Zacken
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(Original post by monk1324)
So I'm not sure about the difference between b) and c) in this question. c) is surely true because the set that contains only one element (which is 7) is obviously a subset of A.
I think b) should be true as well. 7 is an element of a subset of A so 7 must be an element of A as well, right? Would a curly bracket not make any difference in this case?
c isn't true nor is b.

7 is a number
{7} is a set.

A contains the set {7} but does not contain the number 7.
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Notnek
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(Original post by Zacken)
c is true. b isn't.

7 is a number
{7} is a set.

A contains the set {7} but does not contain the number 7.
c isn't true...
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Zacken
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(Original post by notnek)
c isn't true...
Whoops. Edited. Not sure how I made that mistake, I think I meant to type 'a' is true. Thanks for spotting it.
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morgan8002
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(Original post by monk1324)
So I'm not sure about the difference between b) and c) in this question. c) is surely true because the set that contains only one element (which is 7) is obviously a subset of A.
I think b) should be true as well. 7 is an element of a subset of A so 7 must be an element of A as well, right? Would a curly bracket not make any difference in this case?

Also (only answer this one if you can be bothered), for a) as you can see the question asks to justify that 0 is an element of A but it obviously is. It's just there, how would I justify it?
Thanks
a is true obviously because 0 is in A.
b isn't true. {7}\in A, but 7 \not{\in} A. Note the difference: {7} is a set with one element, 7.
c isn't true, similarly to b. 7 is in {7}, but isn't in A, so {7} cannot be a subset of A.
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Notnek
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(Original post by monk1324)
So I'm not sure about the difference between b) and c) in this question. c) is surely true because the set that contains only one element (which is 7) is obviously a subset of A.
I think b) should be true as well. 7 is an element of a subset of A so 7 must be an element of A as well, right? Would a curly bracket not make any difference in this case?

Also (only answer this one if you can be bothered), for a) as you can see the question asks to justify that 0 is an element of A but it obviously is. It's just there, how would I justify it?
Thanks
The set {1,{2},3,4} has four elements (anything separated by commas).

1 is an element of the set but 2 is not. {2} is an element of the set.

A subset is a set containing elements of the set. So {1.{2}} is a subset here but {2} is not (it's an element). {{2}} is a subset because it's a set containing the element {2}.

{1,2} is also not a subset because 2 is not an element of the set.
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Notnek
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(Original post by monk1324)
So I'm not sure about the difference between b) and c) in this question. c) is surely true because the set that contains only one element (which is 7) is obviously a subset of A.
I think b) should be true as well. 7 is an element of a subset of A so 7 must be an element of A as well, right? Would a curly bracket not make any difference in this case?

Also (only answer this one if you can be bothered), for a) as you can see the question asks to justify that 0 is an element of A but it obviously is. It's just there, how would I justify it?
Thanks
For a) I would just describe the set and say that anything separated by a comma is an element.
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shamika
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Once you've got the hang of the question, here's another confusing one:

notnek explained why {2} is not the same thing as {{2}}. What about {{2}} and {{{2}}}?
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