tính giưới hạn sau:....

` lim (\sqrt{4n^{2} + n + 1} - 2n)`

`= lim \frac{(\sqrt{4n^{2} + n + 1} - 2n)(\sqrt{4n^{2} + n + 1} + 2n)}{\sqrt{4n^{2} + n + 1} + 2n}`

`= lim \frac{n+ 1}{\sqrt{4n^{2} + n + 1} + 2n}`

`= lim \frac{1 + \frac{1}{n}}{\sqrt{4 + \frac{1}{n} + \frac{1}{n^{2}}} + 2}`

`= \frac{1}{\sqrt{4 + 0 + 0} + 2}`

`= \frac{1}{4}`

$\color{pink}{\text{$\textit{$\circ$ hungnguyen4269}$}}$