SOLUTION: The height h in feet of an object after t seconds is given by the function h = –16t^2 + 40t + 9. How long will it take the object to hit the ground? Round your answer to the

Algebra ->  Problems-with-consecutive-odd-even-integers -> SOLUTION: The height h in feet of an object after t seconds is given by the function h = –16t^2 + 40t + 9. How long will it take the object to hit the ground? Round your answer to the      Log On


   



Question 75465: The height h in feet of an object after t seconds is given by the function
h = –16t^2 + 40t + 9.
How long will it take the object to hit the ground? Round your answer to the nearest thousandth.

please show work

Answer by ankor@dixie-net.com(22740) 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 = –16t^2 + 40t + 9.
:
When it hits. the ground h = 0 so we have:
-16t^2 + 40t + 9 = 0
:
We can use the quadratic formula: a=-16,b=40,c=9
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
:
x+=+%28-40+%2B-+sqrt%28+40%5E2+-+4+%2A+-16+%2A+9+%29%29%2F%282%2A-16%29+
:
x+=+%28-40+%2B-+sqrt%28+1600+-+%28-576%29%29%29%2F%28-32%29+
:
x+=+%28-40+%2B-+sqrt%28+2176%29%29%2F%28-32%29+
:
x+=+%28-40+-+46.6476+%29%2F%28-32%29+; just worry about the positive solution here
:
x+=+%28-86.6476%29%2F-32
:
x = +2.708 seconds
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