$$\frac{\sqrt{1-\frac{1}{\sqrt{x^2+1}}}}{\sqrt{y^2+1}+\sqrt{z^2+1}}+\frac{\sqrt{1-\frac{1}{\sqrt{y^2+1}}}}{\sqrt{z^2+1}+\sqrt{x^2+1}}+\frac{\sqrt{1-\frac{1}{\sqrt{z^2+1}}}}{\sqrt{x^2+1}+\sqrt{y^2+1}}\leq \frac{3}{2\sqrt{2}}$$
- no matter what yêu thích