The set of ordered pairs that represents exponential decay is when the y-coordinates decrease by a constant positive factor between 0 and 1 as the x-coordinates increase by a constant amount.
In a set of ordered pairs where the x-coordinates increase by a constant amount, the set that represents exponential decay is identified when the y-coordinates decrease by a constant positive factor between 0 and 1. This means that for each step in the x-value, the y-value is multiplied by the same factor (less than 1), resulting in a decrease that is proportional to its current value. This contrasts with linear decay, where y would decrease by the same amount each step, regardless of its current value.