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Math Help - HS Algebra 2-Quadratics, word problem.

  1. #1
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    HS Algebra 2-Quadratics, word problem.

    Please, will you tell me how to get the answer to this? Mostly, I think my issue is with the 10, but I'm not sure.



    In an engineering test, a rocket sled is propelled into a target. The sledís distance d in meters from the target is given by the formula d= -1.5t2+120 where t is the number of seconds after rocket ignition. How many seconds have passed since rocket ignition when the sled is 10 meters from the target?


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  2. #2
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    Quote Originally Posted by dazygrl02 View Post
    Please, will you tell me how to get the answer to this? Mostly, I think my issue is with the 10, but I'm not sure.



    In an engineering test, a rocket sled is propelled into a target. The sledís distance d in meters from the target is given by the formula d= -1.5t2+120 where t is the number of seconds after rocket ignition. How many seconds have passed since rocket ignition when the sled is 10 meters from the target?


    Thanks for taking the time to read my post.
    Hi .

    d=-1.5t^2+120 , so when d=10

    10=-1.5t^2+120

    1.5t^2=110

    t^2=73\frac{1}{3}

     <br />
t=\pm\sqrt{73\frac{1}{3}}<br />

    Then take the positive value .
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  3. #3
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    Okay. Thanks, and now, I'm not doubting the correctness of your answer, but how does that fit into the formula -1.5(x-b/2a^2+c-b^2/4a ? Just because, if when an object is tossed the formula is -16(x-b/2a)^2+c-b^2/4a, I assumed that you had to use the formula up there when the -1.5 is a is given. Sorry.
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