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Math Help - algebra help plz

  1. #1
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    algebra help plz

    find the x intercepts of
    y=2x^2-8x-7
    using completing the square technique



    Find x intercepts of
    y=3x^2-9x+5
    using the quadratic formula
    Last edited by gumi; April 13th 2008 at 11:31 AM.
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  2. #2
    MHF Contributor Mathstud28's Avatar
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    Ok

    Quote Originally Posted by gumi View Post
    find the x intercepts of
    y=2x^2-8x-7
    using completing the square technique



    Find x intercepts of
    y=3x^2-9x=5
    using the quadratic formula
    We would have 2(x-2)2-15=0...solving for x we get x=\frac{\pm{\sqrt{30}+4}}{2}

    and for the second one just use the quadratic formula x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}
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  3. #3
    Junior Member roy_zhang's Avatar
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    Quote Originally Posted by gumi View Post
    find the x intercepts of
    y=2x^2-8x-7
    using completing the square technique



    Find x intercepts of
    y=3x^2-9x=5
    using the quadratic formula
    First please note that the x-intercepts of the quadratic function are the roots of the corresponding quadratic equation. So for these two questions:

    1) solve x for 2x^2-8x-7=0 using completing square technique
    2(x^2-4x+4)-7=8\Rightarrow 2(x-2)^2=15\Rightarrow x=2\pm \frac{\sqrt{30}}{2}

    2) See Mathstud28 comments

    Roy
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  4. #4
    MHF Contributor Mathstud28's Avatar
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    Ok

    Quote Originally Posted by roy_zhang View Post
    First please note that the x-intercepts of the quadratic function are the roots of the corresponding quadratic equation. So for these two questions:

    1) solve x for 2x^2-8x-7=0 using completing square technique
    2(x^2-4x+4)-7=8\Rightarrow 2(x-2)^2=15\Rightarrow x=2\pm \frac{\sqrt{30}}{2}

    2) See Mathstud28 comments

    Roy
    What was wrong with my completing the square's?
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  5. #5
    Junior Member roy_zhang's Avatar
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    Quote Originally Posted by Mathstud28 View Post
    What was wrong with my completing the square's?
    Nothing wrong there.

    Roy
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  6. #6
    MHF Contributor Mathstud28's Avatar
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    Oh

    Quote Originally Posted by roy_zhang View Post
    Nothing wrong there.

    Roy
    were you jsut going through the motions for didactic purposes?
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  7. #7
    Junior Member roy_zhang's Avatar
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    Quote Originally Posted by Mathstud28 View Post
    were you jsut going through the motions for didactic purposes?
    No, I think you are too sensitive here. When I were typing my original response, I saw you just post your reply and I don't want to retype the quadratic formula , this is why i just type please see your comment for part (2). I have no intention to imply that your comment on (1) is not correct.

    We are all here to learn and help.

    Roy
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  8. #8
    MHF Contributor Mathstud28's Avatar
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    Haha

    Quote Originally Posted by roy_zhang View Post
    No, I think you are too sensitive here. When I were typing my original response, I saw you just post your reply and I don't want to retype the quadratic formula , this is why i just type please see your comment for part (2). I have no intention to imply that your comment on (1) is not correct.

    We are all here to learn and help.

    Roy
    I am sorry I didnt intend to sound angry or upset...I was just wondering
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