function f(x) represents the population of bacteria x hours after 9am what does f(2)-f(1)represent

f(2) describes the population of bacteria 2 hours after 9 AM, and f(1) describes the population of bacteria 1 hour after 9 AM. This means that f(2) - f(1) = f(1), so it represents the population of bacteria 1 hour after 9 AM.