Answer: Hello mate!
Exponential growth and decay functions are written as:
F(t) = A₀b^(kt)
We know that A₀ is the initial amount (at the time equal to zero)
b is the growth factor, k is the growth rate, and t is the time (the independent variable)
Note that b is a real and positive number, while A₀ and k can be also negative.
If k is a positive number, then as time grows, the product k*t also increases, and then the factor b^(kt) also increases, and now you have exponential growth.
if k is a negative number, you have the inverse situation, you have an exponential decay.