Inclined asymptote can be found by calculating the limit of Abs(sqrt(x) - 3), divided by x at x->+oo and x ->-oo
$$\lim_{x \to -\infty}\left(\frac{\left|{\sqrt{x} - 3}\right|}{x}\right) = 0$$
Let's take the limitso,
inclined coincides with the horizontal asymptote on the right
$$\lim_{x \to \infty}\left(\frac{\left|{\sqrt{x} - 3}\right|}{x}\right) = 0$$
Let's take the limitso,
inclined coincides with the horizontal asymptote on the left