Question: Evaluate $\lim\_{x\to45} \frac{\sqrt{x+4}-7}{x-45}$

So far I multiply both sides by $x+45$, but I don't know how to finish it.

Please Help!!

Answer: 
Hint:
$$\frac{(\sqrt{x+4}-7)(\sqrt{x+4}+7)}{(x-45)(\sqrt{x+4}+7)}=\frac{1}{\sqrt{x+4}+7}.$$
Use L'Hospital's Rule <http://mathworld.wolfram.com/LHospitalsRule.html>
$$\lim\_{x\rightarrow45}\frac{\sqrt{x+4}-7}{x-45}=\lim\_{x\rightarrow45}\frac{\frac{d}{dx}(\sqrt{x+4}-7)}{\frac{d}{dx}(x-45)}=\frac{1}{14}$$