username5396224
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hi
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Theloniouss
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#2
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Can you show how you got your answer?
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mqb2766
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(Original post by dog25)
a={factors of 12}
b={factors of 18}
d={prime numbers} the universal set is 1 to 25 inclusive
a ∪ b∩d'
for this i got 1,6,12 and 18 but the answer is just 1 and 6 why?And how would you do this PLEASE HELP
Can you upload a pic of the question as well?
Is it
a or b
Or
a and b
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username5396224
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#4
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huh?i copied the question exactly from the sheet
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username5396224
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#5
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hu
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Interea
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Is 12 in b and is 18 in a?
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username5396224
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#7
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yes it says factors of 12 for a and factors of 18 for be between 1 and 25 which 12 and 18 are?
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username5396224
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#8
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i am confused ?what answer did u get
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Interea
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(Original post by dog25)
yes it says factors of 12 for a and factors of 18 for be between 1 and 25 which 12 and 18 are?
Ah sorry misread the question - yeah in that case I don't see why 12 and 18 aren't included, unless the question means factors aside from themselves.
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mqb2766
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(Original post by dog25)
huh?i copied the question exactly from the sheet
It sometimes helps to see the original question.
If it's as you describe, then
a or b and not prime
Would include 12 and 18.
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ghostwalker
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(Original post by dog25)
a={factors of 12}
b={factors of 18}
d={prime numbers} the universal set is 1 to 25 inclusive
a ∪ b∩d'
for this i got 1,6,12 and 18 but the answer is just 1 and 6 why?And how would you do this PLEASE HELP

You asked this question 3 days ago.

The notation a ∪ b∩d' is ambiguous. It could mean (a\cup b) \cap d' or a\cup (b \cap d' ).

Neither of these two options yield {1,6} as the solution set.

The only way I can see to get that solution is via : a\cap b \cap d'

So, I suspect a typo. in the original question.
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username5396224
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no the answer is definitely 1 and 6?
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davros
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(Original post by dog25)
no the answer is definitely 1 and 6?
Not to the question you've posted it isn't!

Also, 9 would be in d' as it is a non-prime number between 1 and 25, and 9 is also a factor of 18 so it would be in b intersect d' and therefore would be in
a union (b intersect d') since by definition this includes all the elements in b intersect d'.

It would also be in (a union b) intersect d' if you interpreted the question in a different way!
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