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    make d the subject of the equation:
    m = (4d)/(x+4)
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    m = (4d)/(x+4)
    m(x+4) = 4d
    d = 0.25m(x+4)

    easy.
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    (Original post by Undry1)
    make d the subject of the equation:
    m = (4d)/(x+4)
    => m(x + 4) = 4d

    => d = (1/4)m(x + 4)
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    bummer. sorry typed it in wrong.
    y=(4d)/(d+4)
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    (Original post by Undry1)
    bummer. sorry typed it in wrong.
    y=(4d)/(d+4)
    y(d + 4) = 4d

    yd + 4y = 4d

    4d - yd = 4y

    d(4 - y) = 4y

    d = 4y/(4 - y)
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    (Original post by Nylex)
    y(d + 4) = 4d

    yd + 4y = 4d

    4d - yd = 4y

    d(4 - y) = 4y

    d = 4y/(4 - y)
    thanks
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    No prob.
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    (Original post by Undry1)
    bummer. sorry typed it in wrong.
    y=(4d)/(d+4)
    I remember first coming across one of these problems at GCSE; none of our class could do it. Once you know that you have to factorise, it's easy!
 
 
 

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