tính \(A=lim\left[n\left(\sqrt{n^2+2}-\sqrt{n^2-1}\right)\right]\)

tính gioi han cua day so:

\(u_n=\dfrac{\left(n+1\right)\sqrt{1^3+2^3+...+n^3}}{3n^3+n+2}\)

Tính:

A= \(lim\dfrac{n+1}{n^2+2n}\)

B= \(lim\left(-2n^3+n^2+2\right)\)

C= \(lim\dfrac{\sqrt{9n^2-n-1}}{4n-2}\)

D= \(lim\dfrac{3^n+5.4^n}{4^n+2^n}\)