A population of fish in a newly dug pond grows according to the equation P=80001+7e-0.9t where time t is given years. In how many years will there be 4000 fish

Question

i need help on putting this formula together

 

Answer 1

p = 80001 + 7e^-.9t

what is the value of t when p = 4000?

 

4000 = 80001 + 7e^-.9t

subtract 80001 from both sides

-76001 = 7e^-.9t

divide both sides by 7

-76001/7 = e^-.9t

take natural log of both sides

 

note: ln(eⁿ) = n

 

ln(-76001/7) = ln(e^-.9t)

ln(-76001/7) = -.9t

divide both sides by -.9

 

t = ln(-76001/7)/(-.9)

 

There seems to be a problem with the information given.  We cannot take the natural log of -76001/7