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Math Help - Simultaneous quadratic and linear equations - yr 11

  1. #1
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    Simultaneous quadratic and linear equations - yr 11

    Anyones help would be greatly appreciated...

    The graphs: y = x^2 - bx - 14 AND y = -9x + c intersect at
    (-1,8) and (-3,10) . Find the values of b and c

    Cheers
    Last edited by steph_r; March 30th 2008 at 02:22 AM. Reason: Written incorrectly
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  2. #2
    Moo
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    Hello,

    I don't know where is b... Nevermind.

    You know that the points (-1,8) and (-3,10) belong to both the graphs.
    So you just have to replace their values in the expressions of the functions.
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  3. #3
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    Quote Originally Posted by Moo View Post
    Hello,

    I don't know where is b... Nevermind.

    You know that the points (-1,8) and (-3,10) belong to both the graphs.
    So you just have to replace their values in the expressions of the functions.
    im terribly sorry i wrote it wrong.. this is how it was supposed to be written..

    y = x^2 + bx - 14 AND y = -9x + c . They intersect at (-1,8) and (-3, 10). Find the values of b and c.

    Thank you.
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  4. #4
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    just substitute (-1,8) and (-3,10) into both equations

    e.g.
    y=9x+c
    at (-1,8)
    8= -9 * -1 +c

    y=9x+c
    at (-3,10)
    10= -9 * -3 +c (*=times)
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