For the period 1985 - 2001, the number y (in millions) of cell phone service subscribers in the U.S. can be modeled by the function y = 0.7x^2 - 4.3x + 5.5 where x is the number of years since 1985. In what year were there 16,000,000 cell phone service subscribers?
Here again, GM....a graph might be the best way to go
y = 0.7x^2 - 4.3x + 5.5
See the graph, here :
This occurs in about the 8th year after 1985 [ in 1993 ]