I've thought about this problem for several days. Here's my take on the answer.
As Rom pointed out, the interval [-(7/2), (1/4)] does indeed make the "log" in the numerator undefined.
But I believe the answer to the problem lies in the denominator. In effect, we have the domain of an "inside" function - (4x-1) - to consider, and the domain of an "outside" function - log(4x-1) - to consider. Note that any values between (1/4) and (1/2) are OK - they just make the denominator negative. But also notice that any values less than (1/4) aren't defined for log(4x-1). And x=(1/2) isn't defined, either.
So, I believe the correct answer to this problem are the two intervals (1/4, 1/2) and (1/2, ∞)
Anybody have another take??