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Math Help - Where did the subtraction sign go?

  1. #1
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    Where did the subtraction sign go?

    I can't get images to upload to this site, so I put the image in my public dropbox.com folder:

    http://dl.dropbox.com/u/19828686/math001.jpg

    There is a minus sign in the first part of this problem. As you see in the picture, the book takes you through three stages to the answer, but I don't understand where the minus sign went. Any ideas? Thanks in advance.
    Last edited by jesse; May 16th 2011 at 06:06 PM. Reason: Nobody is helping me!
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  2. #2
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    I can't get images to upload, either. This is why I try to learn to communicate more effecitvely through the written word.

    Not everyone will open an external link. Try harder to type what you need. Learning just a little LaTeX could help quite a bit.

    We have only volunteers who wander by when they have the time. If you need instant answers, you should consider paying a higher fee than you are charged, here.

    There is no "minus sign" or "subtraction sign" in your problem statement. The technical term for that would be "Unary Minus" or simply "Negative Sign". A "minus sign" (certainly a "subtractino sign") would indicate subtraction and you've none of that. The presence of a negative sign in front of a fraction indicates the fraction is multiplied by -1. Note these:

    (-1)^1 = -1
    (-1)^2 = 1
    (-1)^3 = -1
    (-1)^4 = 1

    It's like a little pulsar!

    Do you now see where your negative sign went?
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  3. #3
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    Thanks for replying... I will take your advice and learn LaTeX: it's worth my while because you folks that hang out here are so helpful. Sorry about the terminology. I do understand! The even exponent is the culprit.
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  4. #4
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    Hi jesse,
    I agree with you. I read (-b^2/a^3)^b as (-1)^b ) ( b^2/a^3)^b so (-1)^b must remain in the answer



    bjh
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  5. #5
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    It's rather hard to read. I took it as (-1)^6, in which case it can go away. We would have to keep (-1)^b unless we know more about 'b'.
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