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Math Help - formula rearrangement

  1. #1
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    formula rearrangement

    Hi,

    having trouble with arranging formulae that have a negative sign. i.e.

    a - bx = m
    - bx = m - a
    x = [m - a][/-b]

    thats my working of the problem

    but the text book answer is: x = [a - m][/b]

    what am I doing wrong?
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  2. #2
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    Quote Originally Posted by nativecat View Post
    Hi,

    having trouble with arranging formulae that have a negative sign. i.e.

    a - bx = m
    - bx = m - a
    x = [m - a][/-b]

    thats my working of the problem

    but the text book answer is: x = [a - m][/b]

    what am I doing wrong?
    You haven't done anything wrong.

    Remember that p - q = -(q - p) and that a negative times/divided by a negative gives a positive.

    So from your working you've ended up with

    x = \frac{m - a}{-b}

     = \frac{-(a - m)}{-b}

     = \frac{a - m}{b}.
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