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Math Help - Quadratic equation

  1. #1
    Newbie Bluerabbits's Avatar
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    Exclamation Quadratic equation

    A stuntman is being shot out of a canon. Heīs following a track that is determinded by this equation:

    y = 1 + 3x - 0,05x^2

    where x meter is the horizontal distance from the canon and y meter is the height.
    Will the stuntman be able to cross a gulch that is 58 metres wide?

    Picture (I drew xD):

    http://i56.tinypic.com/33jjvco.png


    OPS! 56 m bred (swedish word for: width)


    56 m bred = 56 m width
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  2. #2
    Master Of Puppets
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    You mean y  = 1 + 3x - 0.05x^2 ?

    What were your solutions for y=0?
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  3. #3
    Newbie Bluerabbits's Avatar
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    I donīt know how to solve this ...
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  4. #4
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    That's a quadratic equation, as you say, so use the quadratic formula:
    The solutions to ax^2+ bx+ c= 0 are given by
    \frac{-b\pm\sqrt{b^2- 4ac}}{2a}.

    Here, a= -0.05, b= 3, and c= 1.
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  5. #5
    Newbie Bluerabbits's Avatar
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    Quote Originally Posted by HallsofIvy View Post
    That's a quadratic equation, as you say, so use the quadratic formula:
    The solutions to ax^2+ bx+ c= 0 are given by
    \frac{-b\pm\sqrt{b^2- 4ac}}{2a}.

    Here, a= -0.05, b= 3, and c= 1.

    Hi, I have been trying to put this into my calculator but itīs just saying error all the time ...
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  6. #6
    Forum Admin topsquark's Avatar
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    Quote Originally Posted by Bluerabbits View Post
    Hi, I have been trying to put this into my calculator but itīs just saying error all the time ...
    Try it this way. Find b^2 - 4ac. Then take the square root. Then calculate the rest. If you break it apart there's less chance of a calculation error. Just make sure you don't round off the intermediate steps. Keep, say, at least 5 digits.

    -Dan
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