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Question 55108: 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 to reach ground level?
Answer by ankor@dixie-net.com(22740)   (Show Source):
You can put this solution on YOUR website! 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 to reach ground level?
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When the object is at ground level, s(t) = 0; solve for t when s(t) = 0
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-16t^2 + 64t + 80 = 0
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Since we are finding the x intercept (not the max), we can simplify the equation by dividing by -16, then we have an equation that can easily be factored:
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x^2 - 4t - 5 = 0
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(x - 5)(x + 1) = 0
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x = +5 seconds, the positive solution is what we want, obviously
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