A population of flies grows according to the function p (x) = 5 (2) x, where x is measured in weeks. A local spider has set up shop and consumes flies according to the function s (x) = 3x + 2. What is the population of flies after three weeks with the introduced spider?

The answer is 29 flies.

x is the number of weeks. We have 2 weeks, so x = 3

1. Calculate the population of flies after 3 weeks: p (3) = ?

2. Calculate how much flies are eaten by the spider after 3 weeks: s (3) = ?

3. Subtract the number of flies after 3 weeks and eaten flies after three weeks: p (3) - s (3) = ?

1. p (x) = 5 · 2ˣ

p (3) = 5 · 2³ = 5 · 8 = 40

2. s (x) = 3x + 2

s (3) = 3 · 3 + 2 = 9 + 2 = 11

3. p (3) - s (3) = 40 - 11 = 29