Summary of Exponential Growth and Decay

Exponential growth and exponential decay are two of the most common applications of exponential functions.
Systems that exhibit exponential growth follow a model of the form $y={y}_{0}{e}^{kt}.$
In exponential growth, the rate of growth is proportional to the quantity present. In other words, ${y}^{\prime }=ky.$
Systems that exhibit exponential growth have a constant doubling time, which is given by $(\text{ln}2)\text{/}k.$
Systems that exhibit exponential decay follow a model of the form $y={y}_{0}{e}^{\text{−}kt}.$
Systems that exhibit exponential decay have a constant half-life, which is given by $(\text{ln}2)\text{/}k.$

Glossary

doubling time: if a quantity grows exponentially, the doubling time is the amount of time it takes the quantity to double, and is given by $\frac{(\text{ln}2)}{k}$

exponential decay: systems that exhibit exponential decay follow a model of the form $y={y}_{0}{e}^{\text{−}kt}$

exponential growth: systems that exhibit exponential growth follow a model of the form $y={y}_{0}{e}^{kt}$

half-life: if a quantity decays exponentially, the half-life is the amount of time it takes the quantity to be reduced by half. It is given by $\frac{(\text{ln}2)}{k}$