Evaluate lim$_{n\rightarrow\infty}$ $\frac{1-2+3-4+5-...............+\left(-2n\right)}{\sqrt{n^{2}+1}+\sqrt{n^{2}-1}}$
Compute: $\lim_{n \rightarrow \infty}\sqrt{n}(A_{n+1} − A_n)$ where $A_n = \frac{1}{n}(a_1 + a_2 + \cdots + a_n)$