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Math Help - Sets Problem

  1. #1
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    Sets Problem

    Are the following statements true :
    1. A B = A B

    But I think it should be
    A B = A B

    2. A B = U A B
    But I think it should be
    A B = U A B

    3.(A B) B = A iff B A
    But I think it should be
    (A B) B = A iff B A

    Plz tell me I am wrong or book is wrong. Plz give ur answer with reason. I dont want mathematical proof for the correct statements. If possible , plz verify the statement that u say correct or wrong.
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  2. #2
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    Quote Originally Posted by goodone View Post
    Are the following statements true :
    1. A B = A B

    But I think it should be
    A B = A B

    2. A B = U A B
    But I think it should be
    A B = U A B

    3.(A – B) B = A iff B A
    But I think it should be
    (A – B) B = A iff B A

    Plz tell me I am wrong or book is wrong. Plz give ur answer with reason. I don’t want mathematical proof for the correct statements. If possible , plz verify the statement that u say correct or wrong.
    Check the definition of the two subset relations in the source for the questions, some authors use \subset to denote a subset not necessarily a proper subset.

    .
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  3. #3
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    still the problem

    Author is using to denote the proper subset and to denote the subset.
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  4. #4
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    Quote Originally Posted by goodone View Post
    Author is using to denote the proper subset and to denote the subset.
    Then clearly something is wrong, try seeing what happens when A=B to show this (the lefthand sides of the implication hold but the right hand sides do not.

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