Chứng minh:
$$\left ( -a+ 2\,b+ 2\,c \right )^{2}\left ( b+ c \right )^{2}\geqq 12\,bc\left ( a+ b+ c \right )\left ( -a+ b+ c \right )$$
Spoiler
Chứng minh:
$$\left ( -a+ 2\,b+ 2\,c \right )^{2}\left ( b+ c \right )^{2}\geqq 12\,bc\left ( a+ b+ c \right )\left ( -a+ b+ c \right )$$
Spoiler
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