Toán 7 về căn bậc 2

Q

quynhphamdq

Ta có :
$\frac{1}{\sqrt{1}}> \frac{1}{\sqrt{n}}$
$\frac{1}{\sqrt{2}}>\frac{1}{\sqrt{n}}$
$...$
$\frac{1}{\sqrt{n-1}}>\frac{1}{\sqrt{n}}$
$\frac{1}{\sqrt{n}}=\frac{1}{\sqrt{n}}$
\Rightarrow $\frac{1}{\sqrt{1}}+\frac{1}{\sqrt{2}}+...+\frac{1}{\sqrt{n}}$$>\frac{n}{\sqrt{n}}=\sqrt{n}$(đpcm)
 
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