Hello, zsf1990!
Here is another approach.
. .
. .
In this equation:
Which logarithm property is used to change log base 4 to log base 2? Is it just an application of the change of base theorem? Everything else makes sense to me but that.
EDIT: I feel dumb now. I just realized that it's the change of base theorem being used to change the base to log base 2, thus giving a simplified answer.