Tìm các giới hạn sau:
1, $\mathop {\lim }\limits_{}$$\frac{n^2-1}{2n^2+3n+5}+\frac{\sin n}{10^n}$ 2, $\mathop {\lim }\limits_{x \to 0}$$\frac{2x+1-\sqrt{3x^2+1} }{\sin 2x}$
3, $\mathop {\lim }\limits_{x \to -1}$$\frac{x+\sqrt{3+2x} }{x^2-8x-9}$ 4, $\mathop {\lim }\limits_{x \to 2^+}$$\frac{\sqrt{x^2+x-6} }{-x^2+x+2}$
5, $\mathop {\lim }\limits_{}$$\frac{2n^2+3}{n^2+3n+8}+\frac{\cos n}{9^n}$ 6, $\mathop {\lim }\limits_{x \to 0}$$\frac{\sqrt{5x^2+4}-2(x+1) }{\sin 2x}$