Finding limit of fraction with square roots: $\lim_{r\to 9} \frac {\sqrt{r}} {(r-9)^4}$ I have been looking at this for five minutes, no clue what to do.
$$\lim_{r\to 9} \frac {\sqrt{r}} {(r-9)^4}$$

Replacing $r$ by $r-9$,
this becomes
$\lim_{r\to 0} \frac {\sqrt{r+9}} {r^4}
$. 
As was said, the numerator goes to 3
and the denominator goes to 0,
so the quotient goes to $\infty$.
