Cho $x,y,z$ $\geq$ $0$. Chứng minh rằng:
$\frac{1}{x^2+xy+y^2}$ $+$ $\frac{1}{y^2+yz+z^2}$ $+$ $\frac{1}{z^2+zx+x^2}$ $\geq$ $\frac{9}{(x+y+z)^2}$
Cho $x,y,z$ $\geq$ $0$. Chứng minh rằng:
$\frac{1}{x^2+xy+y^2}$ $+$ $\frac{1}{y^2+yz+z^2}$ $+$ $\frac{1}{z^2+zx+x^2}$ $\geq$ $\frac{9}{(x+y+z)^2}$
BẤT ĐẲNG THỨC CHÍNH LÀ THUỐC PHIỆN CỦA TOÁN HỌC
Cho $x,y,z$ $\geq$ $0$. Chứng minh rằng:
$\frac{1}{x^2+xy+y^2}$ $+$ $\frac{1}{y^2+yz+z^2}$ $+$ $\frac{1}{z^2+zx+x^2}$ $\geq$ $\frac{9}{(x+y+z)^2}$
http://diendantoanho...c1b12a2a1geq-9/
"The first analogy that came to my mind is of immersing the nut in some softening liquid, and why not simply water? From time to time you rub so the liquid penetrates better, and otherwise you let time pass. The shell becomes more flexible through weeks and months—when the time is ripe, hand pressure is enough, the shell opens like a perfectly ripened avocado!" - Grothendieck
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