Which function represents exponential decay?

f(x) =1/2 (3/2)^x

f(x) =1/2 (-3/2)^x

f(x) =4 (-2/3)^x

f(x) = 4 (2/3)^x

A quantity is subject to exponential decay if it decreases at a rate proportional to its current value. Symbolically, this process can be expressed by the following differential equation, where N is the quantity and λ (lambda) is a positive rate called the exponential decay. So the function represents a exponential decay is f(x) = 4 (2/3)^x

 

/-/////////looks tough ‍♂️