The population of Arizona was 4.2 million in 2000 and 6.9 million in 2008. If the population grew exponentially, which one of the following models the population as a function of time (in years since 2000)?
Since the population grew by a factor of 1.64 over 8 years, we have
p = 4.2 * 1.64^(t/8)
Since 1.64 = e^0.49 (call it e^.5), we have
p = 4.2 * e^(t/16)