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Homework Help: Set theory

  1. Jan 19, 2014 #1
    1. The problem statement, all variables and given/known data
    I am not sure if set theory is precalc or not but here is my question.

    Find a pair set such that {a} belongs to the set and {a} is not a subset of S.

    3. The attempt at a solution
    So I thought that a set like this would work S = {{a}, b} because {a} belongs to the set, but in order for {a} to be a subset it has to be wrapped in more brackets so {{a}} is a subset. Am I right? If not what did I state that was wrong?
  2. jcsd
  3. Jan 19, 2014 #2
    The example you have chosen is alright ,but the reasoning doesn't looks okay .For {a} to be a subset , 'a' should be an element of the set ,not {{a}} .For example for the set {a,b} , the subsets can be {a,b},{a},{b},ø . For set {{a},b} , the subsets can be {{a},b} , {{a}} ,{b} , ø .
  4. Jan 19, 2014 #3
    Yea I realized my explanation was wrong but ny reasoning was the same as yours
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