toán 8 (làm nhanh hộ mình)

H

huytrandinh

[TEX]M=1-\frac{2}{a}+\frac{2011}{a^{2}}[/TEX]
[TEX]=2011(\frac{1}{2011}-\frac{2}{2011a}+\frac{1}{a^{2}})[/TEX]
[TEX]=2011(\frac{1}{a}-\frac{1}{2011})^{2}+\frac{2010}{2011}[/TEX]
[TEX]\geq \frac{2010}{2011}=>min=\frac{2010}{2011}[/TEX]
[TEX]<=>a=2011[/TEX]
 
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