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Math Help - Binomial coefficients in expansions

  1. #1
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    Binomial coefficients in expansions

    Hey guys,
    Im having trouble with this problem, i dont want a solution just really need some help understanding how to go about looking at this problem and how to start it off.

    Find the coefficient of x^3y^7 in the expansion of (3x-2y)^10

    Thanks
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  2. #2
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    Knowing that \left( {a + b} \right)^n  = \sum\limits_{k = 0}^n {{n \choose k}  a^k b^{n - k} } surely you can answer your one question.
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  3. #3
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    i see, how does the (3x -2y) influence the problem opposed to if u just had (x-y)?

    thanks for the help
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  4. #4
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    Quote Originally Posted by fenix View Post
    i see, how does the (3x -2y) influence the problem opposed to if u just had (x-y)?

    thanks for the help
    a = 3x, b = (-2y), n = 10.

    Now start by getting the general term as suggested by Plato.
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  5. #5
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    I see thanks a lot for the help
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