PT<=>[tex]3-2\frac{x}{\sqrt{2}}.\sqrt{\frac{1-y^2}{2}}-2\frac{y}{\sqrt{2}}.\sqrt{\frac{1-z^2}{2}}-2\frac{z}{\sqrt{2}}.\sqrt{\frac{1-x^2}{2}}=0<=>\frac{x^2}{2}-2\frac{x}{\sqrt{2}}.\sqrt{\frac{1-y^2}{2}}+\frac{1-y^2}{2}+\frac{y^2}{2}-2\frac{y}{\sqrt{2}}.\sqrt{\frac{1-z^2}{2}}+\frac{1-z^2}{2}+\frac{z^2}{2}-2\frac{z}{\sqrt{2}}.\sqrt{\frac{1-x^2}{2}}+\frac{1-x^2}{2} +\frac{3}{2}=0<=>(\frac{x}{\sqrt{2}}-\sqrt{\frac{1-y^2}{2}})^2+(\frac{y}{\sqrt{2}}-\sqrt{\frac{1-z^2}{2}})^2+(\frac{z}{\sqrt{2}}-\sqrt{\frac{1-x^2}{2}})^2+\frac{3}{2}=0[/tex]
MÀ VT>0 với mọi x,y,z thuộc ĐKXĐ
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