`\lim_{n \to +\infty} (2u_n) = 2 \cdot \lim_{n \to +\infty} u_n = 2 \cdot 3 = 6`

`lim_{n \to +\infty} (2u_n + v_n) = 6 + 2 = 8`

Nếu $\lim a_n = a$ và $a \ge 0$ thì $\lim \sqrt{a_n} = \sqrt{a}$

`L = \sqrt{\lim_{n \to +\infty} (2u_n + v_n)} = \sqrt{8}`

$\sqrt{8} = \sqrt{4 \cdot 2} = 2\sqrt{2}$

`->` `\lim_{n \to +\infty} \sqrt{2u_n + v_n} = 2\sqrt{2}`