[tex]\frac{1}{AB^{5}}+\frac{1}{AC^{5}}=\frac{1}{AB^{2}}.\frac{1}{AB^{3}}+\frac{1}{AC^{2}}.\frac{1}{AC^{3}}\leq \sqrt{(\frac{1}{AB^{4}}+\frac{1}{AC^{4}})(\frac{1}{AB^{6}}+\frac{1}{AC^{6}})}< \sqrt{(\frac{1}{AB^{2}}+\frac{1}{AC^{2}})^{2}.(\frac{1}{AB^{2}}+\frac{1}{AC^{2}}).(\frac{1}{AB^{4}}+\frac{1}{AC^{4}}-\frac{1}{AB^{2}.AC^{2}})}< \sqrt{(\frac{1}{AH^{2}})^{2}.\frac{1}{AH^{2}}(\frac{1}{AB^{2}}+\frac{1}{AC^{2}})mũ 2}< \sqrt{\frac{1}{AH^{4}}.\frac{1}{AH^{2}}.\frac{1}{AH^{4}}}=\frac{1}{AH^{5}}[/tex]