SOLUTION: please student in confusion....an object is projected upward from the top of tower. its distance in feet above the ground after t seconds is given by s(t)=-16t^2+64t+80. how

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Question 72977: please student in confusion....an object is projected upward from the top of 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.
Answer by funmath(2933) About Me  (Show Source):
You can put this solution on YOUR website!
an object is projected upward from the top of 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.
It's height will be 0 when it hits the ground, so set the problem = to 0.
0=-16t%5E2%2B64t%2B80
0=-16%28t%5E2-4t-5%29
0%2F-16=-16%28t%5E2-4t-5%29%2F-16
0=t%5E2-4t-5 Factor
0=%28t-5%29%28t%2B1%29 set each factor = to 0 and solve for t.
t-5=0 or t+1=0
t-5+5=0+5 or t+1-1=0-1
t=5 or t=-1
Negative time is meaningless to us, so t=5 seconds.
Happy Calculating!!!!