Final answer:
The population growth of a city increasing annually by 3.2% with a starting population of 86,310 in 2023 is expressed as P(t) = 86,310(1.032)^t, where t is the number of years after 2023.
Step-by-step explanation:
The expression for the population P(t), where t is the number of years after 2023, based on a 3.2% annual increase, is given by the formula P(t) = a(b)^t.
In this case, a represents the initial population and b is the growth factor. Since the city's population in 2023 was 86,310, we take a = 86,310.
The growth factor b is 1 plus the growth rate expressed as a decimal, so b = 1 + 0.032 = 1.032. Therefore, the expression is P(t) = 86,310(1.032)^t.