tìm giới hạn các dãy sau1) limn→+∞√n2+5n√n−n√n−2
2) \mathop {\lim }\limits_{n \to +\infty }\frac{6n}{n-\sqrt{n^2+4n}}
3) \mathop {\lim }\limits_{n \to +\infty }(\frac{2n-3}{\sqrt{2n-1}}-\sqrt{2n-1})
4) \mathop {\lim }\limits_{n \to +\infty }\frac{4^n}{2^n(2.\sqrt{2}^n+2^n)}
5) \mathop {\lim }\limits_{n \to +\infty }\frac{(-2)^n-5^n}{3^{n+1}+5^{n+1}}
6) \mathop {\lim }\limits_{n \to +\infty }\sqrt{\frac{2^{2n}+3^n}{2^{2n+2}-3^{n+1}}}
7) \mathop {\lim }\limits_{n \to +\infty }\frac{sin^n\frac{\Pi }{5}+cos ^n\frac{\Pi }{5}}{sin^n\frac{\Pi }{5}-cos^n\frac{\Pi }{5}}
8) \mathop {\lim }\limits_{n \to +\infty }\frac{\sqrt{9^n-6^n}-3^n}{2^n}