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Posted by **Jen** on Sunday, July 10, 2011 at 11:22pm.

Z = {16, 17, 18, 19, 20}

I'm so confused with this....please help :(

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**Reiny**, Sunday, July 10, 2011 at 11:25pmdo it the same way I just showed you in the other post.

the numbers are between 15 and 20, and they are natural numbers.

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**Jen**, Sunday, July 10, 2011 at 11:27pm{x | 15 < x < 20, x ∈ N} ??

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**Jen**, Sunday, July 10, 2011 at 11:30pmor would it be this {x | 15 < x < 20, x ∈ z} ???

- Math -
**Reiny**, Sunday, July 10, 2011 at 11:38pmThat would work, except say 15<x<21, that was my error.

I would use x ∈ N , since the numbers 15 and 20 were not part of the set Z

or you could say

{x | 16 ≤ x ≤ 20, x ∈ z}

btw, I should have had the original above as

{x | 15 < x < 21, x ∈ N}

The way I had it, the 20 would have been excluded.

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**Jen**, Sunday, July 10, 2011 at 11:44pmSo your saying this question:

Express the following in roster form: Set M is the set of natural numbers between fourteen and nineteen, would be

{x | 15 < x < 21, x ∈ N} ??

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**Reiny**, Sunday, July 10, 2011 at 11:58pmPlease read my replies above including the correction

you want the numbers 16,17,18,19,20

they can be expressed

either as

16≤x≤20 , x∈N

or

15<x<21, x∈N