Answer:
The domain of a function are the values that x can take and the range are the values that take y.
Then,
since the function g(x)=log(x) isn't defined for
, then
log(5-x) doesn't exist when

So, the x can not take the values of x sucht that 5\leq x. Therefore, the domain of f(x) are

Now, observe that the range of f(x) is the set of the real numbers from 5. since 5 is a horizontal asymptote of f.