You may want to review logarithms of products first.

You can also simplify the logarithm of a difference. As you might
expect by now, just as the logarithm of a *product* is
the *sum* of the logarithms, so the logarithm of
a *quotient* is *difference* of the logarithms. For
example, log_{4} (1 / *d*) = log_{4} 1
− log_{4} *d*.