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Thread: Please help on quadradics

  1. #1
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    Please help on quadradics

    3x+3/4-2(x-5)=30


    (2X*2X)-12X+9=0 USE FACTORISATION

    (3X*3X)+13X+2=0 STATE ANSWER TO THREE SIGNIFICANT NUMBERS

    X/8+3X/16=5/X

    (X*X)-2X-6=0
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  2. #2
    Senior Member OReilly's Avatar
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    Quote Originally Posted by sjallim View Post
    3x+3/4-2(x-5)=30


    (2X*2X)-12X+9=0 USE FACTORISATION

    (3X*3X)+13X+2=0 STATE ANSWER TO THREE SIGNIFICANT NUMBERS

    X/8+3X/16=5/X

    (X*X)-2X-6=0
    1)
    $\displaystyle \begin{array}{l}
    3x + \frac{3}{4} - 2(x - 5) = 30 \\
    3x + \frac{3}{4} - 2x + 10 = 30 \\
    x = 20 - \frac{3}{4} \\
    x = \frac{{77}}{4} \\
    \end{array}
    $

    2)
    $\displaystyle \begin{array}{l}
    (2x*2x) - 12x + 9 = 0 \\
    4x^2 - 12x + 9 = 0 \\
    (2x - 3)^2 = 0 \\
    \\
    2x - 3 = 0 \\
    2x = 3 \\
    x = \frac{3}{2} \\
    \end{array}
    $

    3)
    $\displaystyle \begin{array}{l}
    (3x*3x) + 13x + 2 = 0 \\
    9x^2 + 13x + 2 = 0 \\
    x_{1/2} = \frac{{ - 13 \pm \sqrt {97} }}{{18}} \\
    \end{array}
    $

    4)
    $\displaystyle \begin{array}{l}
    \frac{x}{8} + \frac{{3x}}{{16}} = \frac{5}{x} \\
    \frac{{2x + 3x}}{{16}} = \frac{5}{x} \\
    \frac{{5x}}{{16}} = \frac{5}{x} \\
    5x^2 = 80 \\
    x^2 = 16 \\
    x = \sqrt {16} \\
    x = 4 \\
    \end{array}
    $

    5)
    $\displaystyle \begin{array}{l}
    (x*x) - 2x - 6 = 0 \\
    x^2 - 2x - 6 = 0 \\
    x_{1/2} = \frac{{2 \pm \sqrt {4 + 24} }}{2} = \frac{{2 \pm \sqrt {28} }}{2} \\
    \end{array}
    $

    I didn't calculate 3) and 5), hopefully you can do that.
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