I have problems figuring out what was done here:

$\displaystyle \frac{p^3 -q^3}{3(1-pq)}\log\frac{p^3}{q^3} = (p-q) \log\frac{p}{q}$

How does the left side follow?

I can see the lograithm really doesnt play an important role here, so the actual question is how

$\displaystyle \frac{p^3 -q^3}{(1-pq)}=p-q$

tahnk you