Let $a,b,c,d\in \mathbb{R}$ and $\left\{\begin{matrix}

0<a\leq b\leq c\leq d\\

\frac{1}{a}+\frac{2}{b}+\frac{d}{c}\geq 3\\

\frac{2}{b}+\frac{d}{c}\geq 2

\end{matrix}\right.$. Prove that:

$$a^4+b^4+c^4-d^4\leq 17$$

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- February 25th 2013, 05:09 AMleezangqeInequality very hard
Let $a,b,c,d\in \mathbb{R}$ and $\left\{\begin{matrix}

0<a\leq b\leq c\leq d\\

\frac{1}{a}+\frac{2}{b}+\frac{d}{c}\geq 3\\

\frac{2}{b}+\frac{d}{c}\geq 2

\end{matrix}\right.$. Prove that:

$$a^4+b^4+c^4-d^4\leq 17$$ - February 28th 2013, 06:16 AMMINOANMANRe: Inequality very hard
there is something wrong with your post .it looks like chinese to me