Finding: $\lim\limits_{x\to -\infty} \frac{6x^2+5\cos{\pi x}}{\sqrt{x^4+\sin{5\pi x}}}$ 
I'm running into problems with this limit:
  $$\lim_{x\to -\infty} \frac{6x^2+5\cos{\pi x}}{\sqrt{x^4+\sin{5\pi x}}}$$

I've tried using l'Hospitals rule, however we will alway keep the $\cos(\pi x)$ expression, as well for $\sin(5\pi x)$. Also, terms do not cancel out with $\sin$ and $\pi$ since the product with $5$. 
Can anyone give me a hint solving this?
Thanks in advance
Kind regards,

Writing out like
$$\frac{6x^2+5\cos\pi x}{\sqrt{x^4+5\sin 5\pi x}} = \frac{x^2\left(6 + \frac{5\cos \pi x}{x^2}\right)}{x^2\sqrt{1 + \frac{5\sin 5\pi x}{x^4}}}$$
should do the trick.
