1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

I Set Theory

  1. Jun 14, 2016 #1
    Can some please explain to me how to solve these two questions?
    Let A, B and C be any sets, prove that:
    (a) A-B ⊂ A
    (b) (A∩B) complement = A complement ∪ B and (A∪B) complement = A complement∩ B complement.
     
  2. jcsd
  3. Jun 14, 2016 #2

    Math_QED

    User Avatar
    Homework Helper

    We usually write out A\B instead of A -B

    Anyway, start to write down the definitions and see where you get.

    A\B = {x|x ∈ A and x ∉ B}
     
  4. Jun 14, 2016 #3
    Thank you very much for the correction.
    Well.... there are no definitions, it just says let A, B and C be any set, prove that A\B⊂A.
     
  5. Jun 14, 2016 #4

    Math_QED

    User Avatar
    Homework Helper

    Well, look up the definitions! How can you prove something without knowing what the definitions are?
     
  6. Jun 14, 2016 #5
    No definitions bro, just have to use x to prove it... That's why i'm confused.
     
  7. Jun 14, 2016 #6

    PeroK

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    He's talking about the definition of "subset"! As in, what does ##A-B \subset A## actually mean? You can't prove it unless you know what it means.
     
  8. Jun 14, 2016 #7
    oh... okay basically what it means is that all elements of A\B are contained inside A.
     
  9. Jun 14, 2016 #8

    PeroK

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Yes, although more simply and consistently you could say it means:

    Each element of A\B is an element of A.
     
  10. Jun 14, 2016 #9
    Yes, thank you very much sir.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Set Theory
  1. Set Theory (Replies: 1)

  2. Set Theory? (Replies: 2)

  3. Set theory issue (Replies: 1)

Loading...