Astudy is done on the population of a certain fish species in a lake. suppose that the population size p(t) after t years is given by the following exponential function. p(t)=420(0.78)^t does the function represent growth or decay? by what percentage does the population change each year?

Answer
part 1) A decay
part 2) 22%

Explanation
part 1
This is an exponential function.
The number been raised to the power of time is a fraction which is less than 1. This means that as the time increases the fraction is decreasing hence the population.

part 2
The formula for getting the population is P(t)=420×〖0.78〗^t
This means that the current population is 420 and 0.78 is the percentage.
This will be equal to 0.78=78/100
As a percentage =78/100×100=78%
This means that the population decrease by (100-78) = 22%