Final answer:
The relative rate of change of the constant function f(x) = 20 within the interval [0, 20] is zero because the function's graph is a horizontal line with a slope of zero.
Step-by-step explanation:
The question pertains to the concept of the relative rate of change in a function, which is an important concept in calculus. Specifically, we are considering a constant function, f(x) = 20, where x is a real number confined to the interval [0, 20]. Since the function represents a horizontal line, the rate of change of this function is zero everywhere within the defined interval. In other words, the relative rate of change, often expressed as the derivative of the function, is 0 because the slope of a horizontal line is zero and there is no change in the function's value as x varies.