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Math Help - Functional Inequality Proof

  1. #1
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    Functional Inequality Proof

    Let f: \Re \rightarrow \Re

    be a real-valued function defined on the set of real numbers that satisfies:

    f(x+y)  yf(x)+f(f(x))

    for all real numbers x and y. Prove that  f(x)=0 for all x 0.
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  2. #2
    MHF Contributor FernandoRevilla's Avatar
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    Re: Functional Inequality Proof

    See problem 3 here:

    2011 Imo Official Solutions

    Ask your doubts.
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