Cho $a,\,b,\,c,\,d\geqq 0$, chứng minh rằng:
$$\begin{equation}\begin{split} \sum\limits_{cyc}\,\frac{(\,b+ c\,)^{\,2}}{a^{\,a}+ 1}\leqq 8 \end{split}\end{equation}$$
Spoiler
Cho $a,\,b,\,c,\,d\geqq 0$, chứng minh rằng:
$$\begin{equation}\begin{split} \sum\limits_{cyc}\,\frac{(\,b+ c\,)^{\,2}}{a^{\,a}+ 1}\leqq 8 \end{split}\end{equation}$$
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