Final answer:
The domain of the given function, where 0 ≤ x ≤ 20, is [0, 20]. The range is the single value that the function outputs, and if it is a horizontal line with value c, the range would be [c, c].
Step-by-step explanation:
To write the domain and range of the function using interval notation, consider the characteristics of the given function. For the function f(x) which is defined for 0 ≤ x ≤ 20, the graph of f(x) is described as a horizontal line. This implies that the function has a constant value for all x in the domain, and so the range is a single value.
The domain of the function is the set of all possible x values that can be input into the function. Given the restriction 0 ≤ x ≤ 20, the domain in interval notation is [0, 20]. This means that the function is defined and takes on values for all real numbers from 0 to 20, inclusive of both endpoints.
The range of a function is the set of all possible values that the function can output. In the case of a horizontal line, the function outputs the same value for any input within the domain. Therefore, if we denote the constant value by c, the range will be the single value {c}, which in interval notation is still expressed as [c, c].