Final answer:
The function that represents exponential decay is f(x) = 3/4(-1/5)^x (option b). In exponential decay, the base of the exponential term should be between 0 and 1 (exclusive). As x increases, the value of the function decreases exponentially.
Step-by-step explanation:
The function that represents exponential decay is f(x) = 3/4(-1/5)x (option b). In exponential decay, the base of the exponential term should be between 0 and 1 (exclusive). In this case, the base is -1/5, which is between 0 and 1. As x increases, the value of the function decreases exponentially.