Asked by Andrea

The projected number N of Wi-Fi enabled cell phones (in millions) in the U.S. can be modeled by the function N=-0.4x^2+21x+35, where x is the number of years since 2009. If the trend continues, find the year in which the projected number of Wi-Fi enabled cell phones will first reach 150 million? Please help!!!! :(
Answered by Steve
well, just solve
-0.4x^2+21x+35=150

as with most quadratics, it will have two roots. Pick the smallest positive one.
Answered by l
So whats the answer?
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