tìm giới hạn các dãy sau1) $\mathop {\lim }\limits_{n \to +\infty }\frac{\sqrt{n^{2}+5n\sqrt{n}}-n}{\sqrt{n-2}}$
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) $\mathop {\lim }\limits_{n \to +\infty }\frac{\sqrt{9^n-6^n}-3^n}{2^n}$