SOLUTION: The height h in feet of an object after t seconds is given by the function h = –16t2 + 40t + 5. How long will it take the object to hit the ground? Round your answer to the neare

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: The height h in feet of an object after t seconds is given by the function h = –16t2 + 40t + 5. How long will it take the object to hit the ground? Round your answer to the neare      Log On


   

Question 91300: The height h in feet of an object after t seconds is given by the function
h = –16t2 + 40t + 5. How long will it take the object to hit the ground? Round your answer to the nearest thousandth.
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
The height h in feet of an object after t seconds is given by the function
h = –16t2 + 40t + 5. How long will it take the object to hit the ground? Round your answer to the nearest thousandth.
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When the object hits the ground its height is zero.
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-16t^2+40t+5 = 0
16t^2-40t-5 = 0
t = [40+-sqrt(40^2-4*16*-5)]/32
t = [40 +-sqrt1920]/32
Positive answer:
t = [40+43.8178...]/32
t = 2.619.. seconds
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Cheers,
Stan H.