The equations of exponential growth and decay are very similar, both of the form
y = aeᵇˣ
The difference between the two is that growth has a positive factor in the exponent, a positive b. Decay has a negative factor in the exponent, negative b.
The graphs are similar, but kinda mirror images of each other. Exponential growth starts small at the left and grows quickly as we move right with increasing x. Exponential decay starts large and decreases toward zero with increasing x.
Example of simple exponential growth, y=eˣ, simple exponential decay y=e⁻ˣ.