Which of the following indicates a decline in value over time?

The concept of exponential decay directly describes a process where a quantity decreases rapidly over time, illustrating a decline in value. In an exponential decay model, the value diminishes at a rate proportional to its current value, often represented by the function f(t) = a * e^(-kt), where 'a' is the initial amount, 'k' is a positive constant, and 'e' is the base of the natural logarithm.

As time progresses, the function's output decreases towards zero, demonstrating how quantities like population, radioactive substances, or money in a depreciating asset decline in value exponentially. This contrasts sharply with other functions, such as exponential growth, which signifies an increase, linear functions that show a constant rate of change, and quadratic functions, which can exhibit varied behaviors but do not specify a consistent decline like exponential decay. Thus, the accurate reflection of a decline in value over time is captured by the concept of exponential decay.