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# Set theory Watch

1. Let c be the set of all prime natural numbers.
Let e be the segment [7,-7].

Write the following set in list form... C(prime) N D

= [7,-2) U (2,3) U 3,5) U (5,7)

the above answer is from the mark scheme, I have a question about the part in bold there is no ( before the 3 so does this mean 3 is included?

It shouldn't be included?
2. (Original post by khanpatel321)
Let c be the set of all prime natural numbers.
Let e be the segment [7,-7].

Write the following set in list form... C(prime) N D

= [7,-2) U (2,3) U 3,5) U (5,7)

the above answer is from the mark scheme, I have a question about the part in bold there is no ( before the 3 so does this mean 3 is included?

It shouldn't be included?
It's a typo - there should be a bracket there.

3 is prime so it's not included in and therefore writing (2,3) U (3,5) is fine since 3 is not included.

Try to be clearer in future questions: You've mixed up e's and D's and you used 'N' to represent intersection which isn't clear. If you plan to make further threads, I recommend you learn LaTeX or use e,g, this site to copy and paste the symbols.
3. (Original post by notnek)
It's a typo - there should be a bracket there.

3 is prime so it's not included in and therefore writing (2,3) U (3,5) is fine since 3 is not included.

Try to be clearer in future questions: You've mixed up e's and D's and you used 'N' to represent intersection which isn't clear. If you plan to make further threads, I recommend you learn LaTeX or use e,g, this site to copy and paste the symbols.
Ok, will try to make it clearer in the future

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