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Let $x,y,z>0$ and such $xy+yz+xz\ge 2(x+y+z)$,show that $$\dfrac{1}{xy+z}+\dfrac{1}{yz+x}+\dfrac{1}{zx+y}\le\dfrac{1}{2}$$

math110
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1 Answers1

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It's wrong! Try $z\rightarrow0^+$ and $x=y\rightarrow4$.