$6= 3\frac{a^{2}}{3}+2\frac{b^{2}}{2}+c^{2}\geq 6\sqrt[6]{(\frac{a^{2}}{3})^{3}(\frac{b^{2}}{2})^{2}c^{2}}= 6\sqrt[6]{\frac{a^{6}b^{4}c^{2}}{3^{3}2^{2}}}\Rightarrow a^{6}b^{4}c^{2}\leq 3^{3}2^{2}$
và $S=3\frac{a}{3bc}+4\frac{b}{2ca}+5\frac{c}{ab}\geq 12\sqrt[12]{(\frac{a}{bc})^{3}(\frac{b}{2ca})^{4}(\frac{c}{ab})^{5}}=\frac{12}{\sqrt[12]{3^{3}2^{4}}}\frac{1}{\sqrt[12]{a^{6}b^{4}c^{2}}}$
$\Rightarrow S\geq \frac{12}{\sqrt[12]{3^{3}2^{4}}}\frac{1}{\sqrt[12]{3^{3}2^{2}}}=2\sqrt{6}$
Đẳng thức xảy ra $\Leftrightarrow$ a=$\sqrt{3}$,b=$\sqrt{2}$,c=1
- duaconcuachua98 yêu thích