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Math Help - Surjectivity of (x^3) +5

  1. #1
    Member Greengoblin's Avatar
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    Surjectivity of (x^3) +5

    How can I prove the surjectivity of this function? I know I'm trying to prove that for all y in the range there exists an x in the domain such that y=x^3, but I can't think how to go about proving it. Thanks.
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    Quote Originally Posted by Greengoblin View Post
    How can I prove the surjectivity of this function?
    Does \sqrt[3]{{y - 5}} exist fo every y?
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  3. #3
    Member Greengoblin's Avatar
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    Ah yes thanks. I was trying to show it's onto in order to show that it has an inverse, but I didn't think to try it the other way round.
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