2log(a - 2b) = log(a) + log(b)
Using rules of logs: 2log(a - 2b) = log(a - 2b)2
log(a) + log(b) = log(ab)
Therefore: log(a - 2b)2 = log(ab)
---> (a - 2b)2 = ab
a2 - 4ab + 4b2 = ab
a2 - 5ab + 4b2 = 0
(a - 4b)(a - b) = 0
So, either a - 4b = 0 ---> a = 4b ---> a/b = 4
or a - b = 0 ---> a = b (but this is impossible for it will create a log of a negative number)