a population of 75 foxes in a wildlife preserve quadruples in size every 15 years, the function y=75*4^x, where x is the number of 15 year periods, models the population growth. how many foxes will there be after 45 years?
Here's how I think of it: How many "15 year periods" are there in 45 years? Once I know how many fifteen year periods are in 45 years, just plug that number in for x into the function.
45/15 = 3
That means there are 3 fifteen year periods in 45 years.
So after 3 fifteen year periods, there will be 75*43 foxes
That is 75(64) foxes