This document discusses exponential growth and decay functions. It provides examples of how to set up and solve exponential equations to model population growth, fish population decline, and bacterial growth. It also explains how to calculate half-life, which is the time for an exponentially decaying quantity to reduce to half its initial value, and doubling time. Examples are worked through to find the half-life of tritium and a radioactive substance, and to determine the amount of a radioactive substance remaining after a given number of years based on its known half-life. The document concludes with classwork practice problems listed from the textbook.