Dr. Silas studies a culture of bacteria under a microscope. The function b1t=500(1.6)t represents the number of bacteria t hours after Dr. Silas begins her study. Is this an exponential growth or decay? Explain how you know. What does the value 500 represent in this situation? The number of bacteria in a second study is modeled by the function b2t=800(1.6)t. What is the growth rate, r, for this equation? What does the difference of 500 and 800 mean between the two studies?