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Math Help - Plugging in x and y.... really simple stuff but I'm having trouble

  1. #1
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    Plugging in x and y.... really simple stuff but I'm having trouble

    Heres the equation to which where you'll need to plug in x and y
    (-2y)(-2x) - [1 -2x -2y]

    plug these in the equation given above... (x=1/3, y=1/3)
    the answer is 1/3 but idk how the book got that answer...

    here what I have so far after plugging in the x and y into the equation...
    = (-2/3)(-2/3) - [1 - 2/3 - 2/3]
    = 4/9 - [1 - 4/3]..... IM STUCK HERE..... did i do anything wrong??
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  2. #2
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    Re: Plugging in x and y.... really simple stuff but I'm having trouble

    Hey asilvester635.

    You did everything right as long as you evaluate the expression correctly as you have it.
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  3. #3
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    Re: Plugging in x and y.... really simple stuff but I'm having trouble

    So this is what i got next

    = 4/9 - [1/1 - 4/3]
    = 4/9 - [3/3 - 4/3]
    = 4/9 - [-1/3]
    = 4/9 + 1/3
    = 4/9 + 3/9
    = 7/9

    Why didn't i get 1/3 as my answer? did i do anything wrong now?
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  4. #4
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    Re: Plugging in x and y.... really simple stuff but I'm having trouble

    So this is what i got next

    = 4/9 - [1/1 - 4/3]
    = 4/9 - [3/3 - 4/3]
    = 4/9 - [-1/3]
    = 4/9 + 1/3
    = 4/9 + 3/9
    = 7/9

    Why didn't i get 1/3 as my answer? did i do anything wrong now?
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  5. #5
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    Re: Plugging in x and y.... really simple stuff but I'm having trouble

    Using R, (so there is no ambiguity) I plug that in and get:

    > (-2/3)*(-2/3) - (1 - 2/3 - 2/3)
    [1] 0.7777778
    > 7/9
    [1] 0.7777778

    This matches youe answer of 7/9 and not an alternative.
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  6. #6
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    Re: Plugging in x and y.... really simple stuff but I'm having trouble

    oops sorry i forgot to add an exponent of 2 at the end of [1 -2x -2y]... but thanks if figured it out.
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