Nếu \(\mathop {\lim }\limits_{} {\mkern 1mu} {u_n}...

A

- Hướng dẫn giải

$\mathop {\lim }\limits_{} {\mkern 1mu} {u_n} = 9 \Rightarrow \mathop {\lim }\limits_{} {\mkern 1mu} \frac{{2018}}{{\sqrt {{u_n} + 7} }} = \mathop {\lim }\limits_{} {\mkern 1mu} \frac{{2018}}{{\sqrt {9 + 7} }} = 504,5$