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Math Help - Expansion of (x-(3/x^2)^9

  1. #1
    acc
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    Expansion of (x-(3/x^2)^9

    In the expansion of (x-(3/x^2)^9 find the following:

    a) the term containing x6

    b) the constant term

    This is my last question, I swear! :P
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  2. #2
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    Quote Originally Posted by acc View Post
    In the expansion of (x-(3/x^2)^9 find the following:

    a) the term containing x6

    b) the constant term

    This is my last question, I swear! :P
    The general term is  {9 \choose r} x^{9 - r} \left( -\frac{3}{x^2}\right)^r = {9 \choose r} (-3)^r x^{9 - r} x^{-2r} = {9 \choose r} (-3)^r x^{9 - 3r}.

    a) You require the coefficient of the power of x corresponding to 9 - 3r = 6.

    b) You require the coefficient of the power of x corresponding to 9 - 3r = 0.
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