Need Help Understanding Notation With Functions

My guess is that $f(x)$ is a more complicated function, but that, as $x \to \infty$, $f(x)$ behaves like $\sqrt{\frac{(x^2+x)^3}{\pi}} $.

That can mean either $\dfrac{f(x)}{\sqrt{\frac{(x^2+x)^3}{\pi}}} \to 1 $ or $f(x)-\sqrt{\frac{(x^2+x)^3}{\pi}} \to 0 $.

I do not know what the "$\pm$" means, since the term following is monotonically increasing and unbounded.