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Math Help - please help with simple problem

  1. #1
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    please help with simple problem

    please show me how to solve for y

    (4x+y) = (x-y)

    thanks
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  2. #2
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    Hi

    Quote Originally Posted by cornman View Post
    please show me how to solve for y

    (4x+y) = (x-y)

    thanks
    4x +y = x - y

    calculate: -4x on both sides

    4x + y - 4x = x -y - 4x

    0x + y = -3x - y

    y = -3x -y

    calculate: add +y on both sides

    y +y = -3x -y +y

    2y = -3x

    Now divide by 2

    \frac{2y}{2} = \frac{-3x}{2}

    y = \frac{-3x}{2}

    Ok?

    Cheers, Rapha
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  3. #3
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    Thanks Rapha. i didnt think i could subtract terms from the parentheses. what am i missing?
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  4. #4
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    Quote Originally Posted by cornman View Post
    I didnt think i could subtract terms from the parentheses. what am i missing?

    Yes you can, because this is a summation, not a product. These parantheses just matter, if theres another factor like

    3*(4x+y) = -17*(x-y)

    In this case you can't just subtract 4x like

    3*(4x+y) - 4x = 3*y

    This is horribly wrong.


    Not sure I didn't get your point.


    Rapha
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  5. #5
    Senior Member mollymcf2009's Avatar
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    Quote Originally Posted by cornman View Post
    can someone please show me the steps to solve for y for the following?

    (4x+y) = (x-y)

    thanks!
    4x + y = x - y

    4x = x - 2y

    3x = -2y

    y = -\frac{3}{2}x
    Last edited by mr fantastic; February 20th 2009 at 02:34 AM. Reason: No edit - just flagging this reply as having been moved from a duplicate post
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