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For the period 1985 - 2001, the number (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? 

GAMEMASTERX40  Apr 12, 2018
edited by GAMEMASTERX40  Apr 12, 2018
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3+0 Answers

 #1
avatar+85726 
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Here again, GM....a graph might be the best way to go

 

y  = 0.7x^2 - 4.3x + 5.5

 

See the graph, here :

 

https://www.desmos.com/calculator/gguuvypnfx

 

This occurs in about the 8th year after 1985    [ in 1993 ]

 

 

cool cool cool

CPhill  Apr 12, 2018
 #2
avatar+632 
+1

Thanks CPhill! (call me Rick)

GAMEMASTERX40  Apr 12, 2018
 #3
avatar+85726 
+1

OK, Rick  !!!!

 

[ You may have to remind me of your name from time-to-time  !!! ]

 

cool cool cool

CPhill  Apr 12, 2018

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