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Math Help - Need help with sets

  1. #1
    Junior Member
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    Need help with sets

    Hi, I'm having a bit of trouble with the following problems:

    Let S = {−5, −4, −3, −2, −1, 0, 1, 2, 3, 4, 5}. List all of the elements in each of the following sets.

    (a) A=[x∈S l x is even and x is a multiple of 3].

    b) B=[x∈S l if x is odd, then x is a multiple of 5]

    I am really confused, as I'm not sure how to solve this. For a) there is no even number in set S that is also a multiple of 3. I have attempted this question many times without any luck, and would greatly appreciate any help.

    Thanks
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  2. #2
    Member HappyJoe's Avatar
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    As for part (a), you are almost right. There is just one number, which is even and a multiple of 3, namely 0. Certainly 0 is even, and since 3 times 0 is 0 itself, 0 is a multiple of 3.

    So A = {0}.

    EDIT: As for the set B, CaptainBlack is correct over what I wrote, which was:

    As for B, I take the description of B to mean that x is an element of B, if x is odd, and x is a multiple of 5. Only two members of S have this property, namely -5 and 5 (because 1 times 5 is 5, and -1 times 5 is -5).

    So B = {-5,5}.
    Last edited by HappyJoe; September 26th 2010 at 12:17 PM.
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  3. #3
    Grand Panjandrum
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    Quote Originally Posted by spoc21 View Post
    Hi, I'm having a bit of trouble with the following problems:

    Let S = {−5, −4, −3, −2, −1, 0, 1, 2, 3, 4, 5}. List all of the elements in each of the following sets.

    (a) A=[x∈S l x is even and x is a multiple of 3].

    b) B=[x∈S l if x is odd, then x is a multiple of 5]

    I am really confused, as I'm not sure how to solve this. For a) there is no even number in set S that is also a multiple of 3. I have attempted this question many times without any luck, and would greatly appreciate any help.

    Thanks
    B consists of all even elements of S and those odd elements which are multiples of 5.

    B=[x∈S l if x is odd, then x is a multiple of 5] reads as:

    B is the set of elements x of S such that if x is odd it is a multiple of 5.



    CB
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