Đề bài

Tính các giới hạn sau:

a) $\mathop {\lim }\limits_{x \to  + \infty } \frac{{9x + 1}}{{3x - 4}};$           

b) $\mathop {\lim }\limits_{x \to  - \infty } \frac{{7x - 11}}{{2x + 3}};$           

c) $\mathop {\lim }\limits_{x \to  + \infty } \frac{{\sqrt {{x^2} + 1} }}{x};$

d) $\mathop {\lim }\limits_{x \to  - \infty } \frac{{\sqrt {{x^2} + 1} }}{x};$              

e) $\mathop {\lim }\limits_{x \to {6^ - }} \frac{1}{{x - 6}};$            

g) $\mathop {\lim }\limits_{x \to {7^ + }} \frac{1}{{x - 7}}.$