Question

Вычислить $\lim_{n \to \infty} \frac{11(n+3)!-n!}{n((n+2)!-(n-1)!)}$

Answer 1

$\displaystyle \lim_{n \to \infty}\frac{11(n+3)!-n!}{n\Big((n+2)!-(n-1)!\Big)}=\lim_{n \to \infty}\frac{n!\Big(11(n+1)(n+2)(n+3)-1\Big)}{n\cdot (n-1)!\Big(n(n+1)(n+2)-1\Big)}=\\ \\ \\ =\lim_{n \to \infty}\frac{n!\Big(11(n+1)(n+2)(n+3)-1\Big)}{n!\Big(n(n+1)(n+2)-1\Big)}=\lim_{n \to \infty}\frac{11(n+1)(n+2)(n+3)-1}{n(n+1)(n+2)-1}=\\ \\ \\ =\lim_{n \to \infty}\frac{11\left(1+\frac{1}{n}\right)\left(1+\frac{2}{n}\right)\left(1+\frac{3}{n}\right)-\frac{1}{n^3}}{1\cdot \left(1+\frac{1}{n}\right)\left(1+\frac{2}{n}\right)-\frac{1}{n^3}}=11$