SOLUTION: the height, h, of the rocket after t seconds is given by the equation h=-16t^2+120t+30. how long after the rocket is launched will it be 20 feet from the ground.
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Question 644717: the height, h, of the rocket after t seconds is given by the equation h=-16t^2+120t+30. how long after the rocket is launched will it be 20 feet from the ground. Answer by nerdybill(7384) (Show Source):
You can put this solution on YOUR website! the height, h, of the rocket after t seconds is given by the equation h=-16t^2+120t+30. how long after the rocket is launched will it be 20 feet from the ground.
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Set h to 20 and solve for t:
h=-16t^2+120t+30
20=-16t^2+120t+30
0=-16t^2+120t+10
0=-8t^2+60t+5
0=8t^2-60t-5
solving for t using the quadratic formula yields:
t = {7.58, -0.08}
throw out the negative solution (extraneous) leaving:
t = 7.58 secs
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Details of quadratic formula follows:
