Answer
$$\sqrt {5}$$
Work Step by Step
Given $$\lim _{x \rightarrow \infty}\frac{\sqrt {5x^2-2}}{x+3 } $$
Then
\begin{align*}
\lim _{x \rightarrow \infty}\frac{\sqrt {5x^2-2}}{x+3 } &=\lim _{x \rightarrow \infty}\frac{\sqrt {5x^2/x^2-2/x^2}}{x/x+3/x } \\
&=\lim _{x \rightarrow \infty}\frac{\sqrt {5 -2/x^2}}{1+3/x }\\
&= \sqrt {5}
\end{align*}