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Math Help - Contradiction Proof- injection, Infinite Sets

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    Post Contradiction Proof- injection, Infinite Sets

    Suppose that there is an injection f: Z+->X. Prove by contradiction that x is an infinite set.
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    Quote Originally Posted by Laurali224 View Post
    Suppose that there is an injection f: Z+->X. Prove by contradiction that x is an infinite set.
    The solution depends on two things.
    What are you using for the definition of infinite set?
    What other theorems do you have to use?

    I will say that proof by contradiction of this likely uses the fact that the composition of two injections is an injection.
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