Tính lim( căn(4n^2+2n-1)-2n+3) Giúp mình câu này với ạ.

$\lim[\sqrt{4n^2+2n-1}-(2n-3)]$

$=\lim\dfrac{4n^2+2n-1-(4n^2-12n+9)}{\sqrt{4n^2+2n-1}+2n-3}$

$=\lim\dfrac{14n-10}{\sqrt{n^2\Big( 4+\dfrac{2}{n}-\dfrac{1}{n^2}\Big)}+2n-3}$

$=\lim\dfrac{14-\dfrac{10}{n} }{ \sqrt{4+\dfrac{2}{n}-\dfrac{1}{n^2}} +2-\dfrac{3}{n}}$

$=\dfrac{14}{\sqrt4+2}$

$=\dfrac{7}{2}$