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Math Help - Proving a set question with three variables

  1. #1
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    Proving a set question with three variables

    Hey guys. New to the math forum. I'm having trouble proving this question. If someone can give just a guide on how to start it, that would assist me with this question and 4 others hopefully.

    Let A, B, C be sets. Show that (A∪ B) ⊆ (A ∪ B ∪ C)


    I started to to prove the right side by switching the parenthesis, using Associative Law. I used x e A or x e B or x e C (or = the logic upside down carrot symbol)
    What do I do from their to prove the left side? Thanks for any input.
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  2. #2
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    Re: Proving a set question with three variables

    Can you show that X \subset X \cup C ? Is it obvious why that's true?

    If yes, then look again at (A \cup B) \subset (A \cup B \cup C).
    Thanks from inflames098
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  3. #3
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    Re: Proving a set question with three variables

    i guess i was making it to complicated. i see how that will work. thanks man.
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