Homework Help: Math Help

Posted by Miguel on Thursday, March 24, 2011 at 11:29am.

Mobile ad spending. The amount spent worldwide in advertising on mobile devices can be estimated by f(x) =0.4x^2+0.01x+0.9. Where x is the number of years after 2005 and f(x) is in billions of dollars. When will worldwide mobile ad spending reaches $41 billion?

Math Help - Reiny, Thursday, March 24, 2011 at 11:51am
solve 41 = .4x^2 + .01x + .9
multiply by 100
40x^2 + x + 90 = 4100
40x^2 + x - 4010 = 0
x = (-1 ą √641601)/80 = 10 or a negative

it will take 10 yrs

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