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Math Help - Quadratic Equations

  1. #1
    Futix
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    Quadratic Equations

    A - y = x2 – 4x – 4 = 0

    B - y = 12x2 + 5x + 1 = 0

    C - y = -23x2 + 7x -4 = 0

    D - y = 3x2 – x -10 = 0

    E - y = 30x2 + 5x – 7 = 0

    I've done these already but my Teacher said I done them wrong, I got to show workings or something, I don't have a Clue what he is on about, I have the formulae but don't know how to display on forum

    *All the Bold numbers are superscript, again, I don't know how to display on forum, this work has to be Friday, not that important, but don't have time to do it again.
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  2. #2
    Forum Admin topsquark's Avatar
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    Quote Originally Posted by Futix View Post
    A - y = x2 – 4x – 4 = 0

    B - y = 12x2 + 5x + 1 = 0

    C - y = -23x2 + 7x -4 = 0

    D - y = 3x2 – x -10 = 0

    E - y = 30x2 + 5x – 7 = 0

    I've done these already but my Teacher said I done them wrong, I got to show workings or something, I don't have a Clue what he is on about, I have the formulae but don't know how to display on forum

    *All the Bold numbers are superscript, again, I don't know how to display on forum, this work has to be Friday, not that important, but don't have time to do it again.
    I'll write the first one out to show you how to do it (without all the fancy LaTeX.)
    I don't know if you are doing complete the square or quadratic formula. Since you are supposed to show your work, I'll assume completing the square.

    x^2 – 4x – 4 = 0 <-- (x^2 indicates x to the second power)

    x^2 - 4x = 4

    x^2 - 4x + 4 = 4 + 4

    (x - 2)^2 = 8

    x - 2 = +/- sqrt(8) <-- (sqrt(8) is the square root of 8 and +/- is the "plus-minus" symbol)

    x = 2 +/- 2*sqrt(2) <-- (3*4 is three times four)

    Why don't you show us what you did.

    -Dan
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  3. #3
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    "show workings" - I think he means just write all of you steps instead of skipping straight to the answer. Example;

    A) x^2-4x-4=0

    \implies x=\frac {-b\pm \sqrt{b^2-4ac}}{2a}

    \implies x=\frac {4\pm \sqrt{(-4)^2-(4 \cdot -4)}}{2}

    Then just go from there
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