SOLUTION: An object is projected upward from the top of a tower. Its distance in feet above the ground after t seconds is given by s(t)=-16t^2+64t+80. How many seconds will it take to reach

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Question 31848This question is from textbook
: An object is projected upward from the top of a tower. Its distance in feet above the ground after t seconds is given by s(t)=-16t^2+64t+80. How many seconds will it take to reach ground level? This question is from textbook

Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
When it reaches ground level its height above the ground will be zero.
So, write -16t^2+64t+80=0
-16(t^2-4t+5)=0
(t-5)(t+1)=0
t=5 seconds or t=-1 second
The answer you want is t=5 seconds
Cheers,
Stan H.