The table gives the cumulative sales of iPods since their
introduction.
Cumulative iPod Sales
Year
Sales
(million iPods)
2003
1.22
2004
5.136
2005
27.833
2006
69.342
2007
118.572
2008
173.8
(a) Find the function for the quadratic model that gives sales
in million iPods, where x is the number of years
after 2003, with data from
0 ≤ x ≤ 5.
(Round all numerical values to three decimal
places.)
s(x) =
million iPods
(b) Write the derivative for the sales model. (Round all numerical
values to three decimal places.)
s'(x) =
million iPods per year
(c) Calculate the rate of change of cumulative sales in 2007.
(Round your answer to three decimal places.)
million iPods per year
Interpret the rate of change of cumulative sales in 2007.
(Round your answer to three decimal places.)
In 2007, cumulative iPod sales
were ---Select--- increasing decreasing by million
per year.