Improper Integrals

I'm trying to evaluate the integral:

$\int_o^\infty \frac{1}{(x+3)^3} dx[br]$

So I get that the integration itself is reverse chain rule and very simple, however I'm not sure how to express the result of the integral as $x$ tends to infinity. Please could someone give me some pointers? Thanks.

replace the infinity with a leter say k
carry the integration with limits
get answer in terms of k
let k tend to infinity


look at 3 examples to see my notation for this type of work

improper_integrals.pdf

Okay so I replaced infinity with k and integrated to get:

$[br]\displaystyle\lim_{k\to \infty} \left[\frac{-1}{2}(k+3)^{-2} + \frac{1}{18}\right][br][br]$

What would I write for my final answer for this? Would I just say that it tends to infinity?

write it as 1/(x+3)²
then as k tens to infinity 1/(x+3)² tends to zero
so 1/18

Sorry, I was half asleep when I wrote that. Yeah, that makes sense, thanks for helping.