How does $\frac{p}{\sqrt{kp - p^2}}$ become $-\frac12 \left( \frac{k-2p}{\sqrt{kp - p^2}} - \frac{k}{\sqrt{kp - p^2}}\right)$?

Question

This is a trivial question, but could someone explain how $$\frac{p}{\sqrt{kp - p^2}}$$ was expanded to the following? $$-\frac12 \left( \frac{k-2p}{\sqrt{kp - p^2}} - \frac{k}{\sqrt{kp - p^2}}\right)$$