Question

Tìm giới hạn của giá trị: 

\(lim\left(\sqrt{n^2+2n}-\sqrt{n^2-2n}\right)\)

Answer 1

\(\lim\limits\left(\sqrt{n^2+2n}-\sqrt{n^2-2n}\right)\)

\(=\lim\limits\dfrac{n^2+2n-n^2+2n}{\sqrt{n^2+2n}+\sqrt{n^2-2n}}\)

\(=\lim\limits\dfrac{4n}{\sqrt{n^2+2n}+\sqrt{n^2-2n}}\)

\(=\lim\limits\dfrac{4}{\sqrt{1+\dfrac{2}{n}}+\sqrt{1-\dfrac{2}{n}}}\)

\(=\dfrac{4}{1+1}=\dfrac{4}{2}=2\)