There is no "equation" to "solve"; there is only a question to be answered.
Please learn to speak (and write) proper English.
Presumably the function is
For completeness, we will assume b>1....
The DOMAIN of the function is x>0, because the logarithm of 0 or a negative number is undefined.
The RANGE is all real numbers:
As x gets closer and closer to its lower bound of 0, the logarithm becomes more negative, without bound.
And as x gets very large, the logarithm becomes more positive without bound.