Using data from 2010 and projected to 2016, the number of millions of U.S. cell phone users can be described by
Y = - 0.187x2 + 5.71x + 232
where x is the number of years past 2010.
(a) Use a table to determine a viewing window that shows a complete graph of this model for the years from 2010 to 2016. State the window used.
(b) Graph this equation.
(c) For years beyond 2016, does this graph increase or decrease? (Look at this graph in a window that includes several of these years.) Explain why this means the model eventually will not accurately describe the relationship between the number of cell phone users and the year.