Final answer:
In the context of a function f from A to B, set A is known as the domain of f, consisting of all input values that f can accept.
Step-by-step explanation:
If f is a function from A to B, A is referred to as the domain of the function f. The domain consists of all the possible input values that the function f can accept. So when we say that f is a function from A to B, we mean that every element in A has a unique image in B through the function f. In the context of the graph of f(x), which is a horizontal line, this means that every x value between 0 and 20 is included in the domain, and they are all mapped to the same value in B because the graph is a horizontal line.
The domain of a function is the set of all possible input values, also known as the independent variable. In this case, A is a nonempty set representing the range of x-values from 0 to 20.
For example, if we have a function f(x) = x^2, the domain would be all real numbers since any real number can be squared. However, in this specific case, the function is a horizontal line, so the domain is restricted to the range of x-values from 0 to 20.