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Math Help - Help evaluating an expression

  1. #1
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    Help evaluating an expression

    It's embarrassing that I can be thrown off by such a seemingly simple question, but I really cannot understand why one of my methods isn't working.
    Question: Evaluate 9x2y+3y4 when x=4 and y=-2. When I do ((9*42)-2)+(3*-24) I get -336 but the correct answer is -240.
    When I use the graphic calculator and just store x as 4 and y as -2 it gives me the -240. Help?
    Last edited by MostLikelyNeedsHelp; October 22nd 2012 at 03:47 AM.
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  2. #2
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    Re: Help evaluating an expression

    Hi There,

    Iíve managed to get -240 by doing this:

    9x2y + 3y4

    When x=4 and y=-2 then:

    = 9*42*-2 + 3*-24

    = 9*16*-2 + 3*16

    = -288 + 48

    = -240

    Hope this helps?
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  3. #3
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    Re: Help evaluating an expression

    Thanks a lot. I needed the (-2)4 as (-24) is wrong obviously. Don't know how I missed.
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