Đề bài

Tìm các giới hạn sau:

a) $\lim \frac{{3n - 1}}{n}$                                                   

b) $\lim \frac{{\sqrt {{n^2} + 2} }}{n}$      

c) $\lim \frac{2}{{3n + 1}}$                                                     

d) $\lim \frac{{\left( {n + 1} \right)\left( {2n + 2} \right)}}{{{n^2}}}$