D
devil_l0v3_angle


Chứng minh rằng
[TEX]ab + bc + ca \leq a^2+b^2+c^2 < 2(ab+bc+ca)[/TEX]
Chú ý latex
[TEX]ab + bc + ca \leq a^2+b^2+c^2 < 2(ab+bc+ca)[/TEX]
Chú ý latex
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