Final answer:
The domain of the function f(2) = 5a + 7, which seems to be a part of a constant function defined from 0 to 20, is actually the set of all real numbers since it's a polynomial in 'a'. The correct domain is represented in interval notation as (-[infinity], [infinity]).
Step-by-step explanation:
The question asks for the domain of a given function, which refers to the set of all possible input values (x-values) for which the function is defined. In this case, the given function is f(2) = 5a + 7. However, the function of f(x) in the context appears to be a constant function with additional information about it being defined from 0 to 20. Therefore, the correct domain, in interval notation for the constant function f(x), where it's restricted between x = 0 and x = 20, would be [0, 20].
But we need to address f(2) which will be the value of the function when x equals 2. This does not alter the domain, which consists of all real numbers that x can take, leading to the correct answer being (−[infinity], [infinity]), which is an unbounded interval representing all real numbers.