Here you go! Hope this helps!
Birmingham and Montgomery both have a state sales tax rate of 4 percent and a local tax rate of 6 percent – although the report notes that part of Birmingham lies in Shelby County, meaning the combined rate is only 9 percent in some parts of the city.
For this case, we must indicate which of the given functions is not defined for
By definition, we know that:
has a domain from 0 to infinity.
Adding or removing numbers to the variable within the root implies a translation of the function vertically or horizontally. For it to be defined, the term within the root must be positive.
Thus, we observe that:
is not defined, the term inside the root is negative when
.
While
if it is defined for 
, your domain is given by all real numbers.
Adding or removing numbers to the variable within the root implies a translation of the function vertically or horizontally. In the same way, its domain will be given by the real numbers, independently of the sign of the term inside the root.
So, we have:
with x = 0:
is defined.
with x = 0:
in the same way is defined.
Answer:

Option b
3/4 is the simplified version of 9/12