

Biết [tex]a,b,c>0[/tex], [tex]ab+bc+ca=1[/tex]. Chứng minh rằng:
[tex]\frac{a}{\sqrt{1+a^{2}}}+\frac{b}{\sqrt{1+b^{2}}}+\frac{c}{\sqrt{1+c^{2}}}\leq \frac{3}{2}[/tex]
[tex]\frac{a}{\sqrt{1+a^{2}}}+\frac{b}{\sqrt{1+b^{2}}}+\frac{c}{\sqrt{1+c^{2}}}\leq \frac{3}{2}[/tex]