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V

vodichhocmai

[TEX]y=x+\frac{11}{2x}+\sqrt{4\(1+\frac{7}{x^2}\)}[/TEX] Tìm GTNN chứ em ?

[TEX]\red note:\ \ \(1+\frac{7}{x^2}\)\(1+\frac{7}{9}\):=\(1+\frac{7}{3x}\)^2+\(\frac{\sqrt{7}}{3}-\frac{\sqrt{7}}{x}\)^2\ge \(1+\frac{7}{3x})^2[/TEX]

[TEX]\righ 4\(1+\frac{7}{x^2}\) \ge \frac{9}{4} \(1+\frac{7}{3x})^2 [/TEX]

[TEX]\righ y =x+\frac{11}{2x}+\sqrt{4\(1+\frac{7}{x^2}\)} \ge x+\frac{11}{2x}+\frac{3}{2}(1+\frac{7}{3x})[/TEX]

[TEX]\ \ \ \ =x+\frac{9}{x}+\frac{3}{2}= \(\sqrt{x}-\frac{3}{\sqrt{x}}\)^2+\frac{15}{2}\ge \frac{15}{2}[/TEX]
 
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T

tuyetkhongtan

anh giai thich cho em hai dong dau nhan voi (1+7/9 ) lam ji a .anh noi ro hon mot teo nua di a em chua hieu lam
 
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