Chapter 4 - Exponential Functions - 4.1 Introduction to the Family of Exponential Functions - Exercises and Problems for Section 4.1 - Exercises and Problems - Page 146: 30

$O(t) =1\cdot (0.98)^t $

The problem describes an exponential function with the following parameters. \begin{equation} \begin{aligned} a&= 1\\ r&= 2\%= 0.02\\ b&=1-r = 0.98\\ \end{aligned} \end{equation} Hence, a model of the Organism due to pollution of the lake in 2015 is \begin{equation} \begin{aligned} O(t)&= a\cdot b^t\\ &= 1\cdot (0.98)^t\\ \end{aligned} \end{equation}