.Find an explicit formula for the beetle population after n weeks and After how many weeks will the beetle population reach 219?

Question

A population of beetles are growing according to a linear growth model. The initial population (week 0) is , and the population after 6 weeks is 

.Find an explicit formula for the beetle population after  weeks.

 = ______

 After how many weeks will the beetle population reach 219?  ________ weeks

Answer 1

initial beetle population = 9

in 6 weeks it reaches 69

the population increase is linear

each week it increases by (69-9)/6 = 10 beetles

P(n) = 9 +10n

219 = 9+10n

210 = 10n

n = 21 weeks to reach 219 beetles