Radicals in a fraction: simplification I cannot for the life of me figure out how this fraction got simplified. Please tell me how the first fraction got simplified into the second one. I've provided initial fraction and its simplified answer: 
$$
-\frac{p \cdot (-1 /(2\sqrt{517-p}) )}{\sqrt{517-p}} = \frac{1}{2(517-p)}
$$

$$ -\frac{p \cdot \frac{-1}{2\sqrt{517-p}}}{\sqrt{517-p}} \\\\$$
$$ -\frac{p \cdot -\frac{1}{2\sqrt{517-p}}}{\sqrt{517-p}} \\\\$$
$$ --\frac{p \cdot \frac{1}{2\sqrt{517-p}}}{\sqrt{517-p}} \\\\$$
$$ \frac{p \cdot \frac{1}{2\sqrt{517-p}}}{\sqrt{517-p}} \\\\$$
$$ \frac{\frac{p}{2\sqrt{517-p}}}{\sqrt{517-p}} \\\\$$
$$ \frac{p}{2\sqrt{517-p} \cdot \sqrt{517-p}} \\\\$$
$$ \frac{p}{2(517-p)} \\\\$$
Which step does not make sense to you?
