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Prove that there is no function $f : \mathbb{R}^+ → \mathbb{R}^+$ such that $$f(x)^2 ≥ f(x + y)(f(x) + y)$$ for all $x, y > 0$.

I can't think of a way of solving this.

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    Would you mind to gives us a source for this problem?2012-05-24

1 Answers 1