Tìm các giới hạn sau:
1, lim\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}