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Math Help - -x^2

  1. #1
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    -x^2

    I'm sure this has been dealt with before, but I couldn't find an answer.

    I remember having a discussion with a math professor a while back on solving -x^2, leaving it in disagreement. I was suddenly reminded that it remained unsolved in my mind, so I ask you all now.

    In particular, the portion of the problem was to simplify -3^2. It was obvious in my mind that it should be -9, but I was told that it is in fact 9. Now, we had a fairly long discussion on it, but the point came down to whether it was a minus sign in front, and implicitly 0 - 3^2, or whether it indicated -3.

    Perhaps I'm looking at it from more of a CS perspective, but I would have assumed (or liked to believe) that unless it was emphasized with parenthesis, that the minus sign should be separate.

    What do you all think?
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  2. #2
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    The standard order of operations used in simplifications is, from first to last:
    Parentheses, Exponents, Multiplication, Division, Addition, Subtraction

    Sidenote: multiplication and division have equal precedence, so you can alternate their ranks.

    As for your particular question:

    -3^2 = -1 \times 3^2 = -1 \times 9  = -9
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  3. #3
    Senior Member Stroodle's Avatar
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    I've always been taught that:

    -3^2=-9 and (-3)^2=9

    otherwise how would you tell the difference in a problem like: -3^2-2
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  4. #4
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    Quote Originally Posted by Stroodle View Post
    edit* oops. double post...
    Just the placement of the negative sign. Its more harder in speech. Look for the pause. But it maths, whenever the equation is just -3^2, the answer is -9. Technically the equation is -1*3^2. If you use your order of operations, the power/exponent comes before the multiplication of -1. Therefore the equation reads -(3^2). If the -3 is in brackets then we do the brackets then the power.
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