The range of a function f(x) are all the possibles values that f(x) can take. So in the function of the question it doesn't matter what value takes x, f(x) is always going to be a positive number. For example:
f(0)==1
f(-1)==1/4
f(2)==16
Then, the range of f(x) is all positive real numbers.
The rules of logarithmic functions require the two log functions to have the same base. If they do not have the same base, you cannot apply any of the rules.
