A biologist puts an initial population of 500 bacteria into a growth plate. The population is expected to double every 4 hours. Which of the following equations gives the expected number of bacteria, n, after x days? (24 hours = 1 day)

1212An exponential function can be written in the form where a is the initial amount, b is the growth factor, and t is the time. In the scenario described, the variable y can be substituted with n, the total number of bacteria, and the initial amount is given as 500, which yields . The growth factor is 2 because the population is described as being expected to double, which gives the equation . The population is expected to double every 4 hours, so for the time to be x days, x must be multiplied by 6 (the number of 4-hour periods in 1 day). This gives the final equation .