Answer:
For a general function f(x), the domain is the set of the possible values of x that we can input in the function.
The trick to find the domain is first to assume that the domain is the set of all real numbers, and then let's try to find the values of x that cause a problem in the function. (If the graph is cut in some value of x, such that it ends with an open or a closed point, then these values define the domain).
Such that one of these problems can be like x = 1 in the function:
g(x) = 1/(x - 1)
Because that value causes the denominator to be equal to zero, then the domain of that function will be the set of all real numbers except the value x = 1.
In this case, we have:
f(x) = x^2 - 4
There is no value of x that causes a problem for this function, then the domain is the sett of all real numbers.
Correct option D.
