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Math Help - Binomial Expansion

  1. #1
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    Binomial Expansion

    The question is:

    Which term in the expansion of ( [1/3x^2] - x )^15 is the constant term?

    Sorry about not creating the equation properly.

    Could anyone provide a moderately in-depth answer and how to approach the question?
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  2. #2
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    Re: Binomial Expansion

    Is this \displaystyle \left( \frac{1}{3}x^2 - x \right) ^{15} or \displaystyle \left( \frac{1}{3x^2} - x \right) ^{15} ?
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  3. #3
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    Re: Binomial Expansion

    The second one. Sorry for the trouble haha!
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  4. #4
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    Re: Binomial Expansion

    Binomial Expansion-binomial-20-mar-13.png
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  5. #5
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    Re: Binomial Expansion

    In the 5th line that you wrote, where does the [(-1)^r][x^r] come from? (-x)^15 ??
    If so, how?

    Other than that I seem to understand it though! Thanks for making that!!!

    *edit
    NVM It seems there was a mistake but I know what happened now! Thanks for the solution. +rep
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  6. #6
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    Re: Binomial Expansion

    It is a typing error. It should be (-x)^r= (-1)^r * x^r
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