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Homework Help: Combinations and Permutations Question

  1. Apr 4, 2010 #1
    1. The problem statement, all variables and given/known data

    1) What is the coefficient of x^43 in the expansion of [(2/x^2) − x3)^16?
    (2) What is the coefficient of x^14y^12 in the expansion of (3x − 2y)^26?

    2. Relevant equations

    Binomial Expansion

    3. The attempt at a solution

    For (1),

    I started out like this:

    (16 0) ( 2/x^2)^16 (-x^3)^0 + (16 1) (2/x^2)^15 (-x^3)^1 +....+ (16 16) (2/x^2)^0 (-x^3)^16.

    Is that how we do it?
    Do we do the same for (2)?
  2. jcsd
  3. Apr 4, 2010 #2


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    Science Advisor
    Homework Helper

    Hi snaidu228! :smile:

    (try using the X2 tag just above the Reply box :wink:)
    Yes, that's it (except, of course, you only need the one term that has x43). :wink:

    (and similarly for (2))
  4. Apr 5, 2010 #3
    Thank you very much!
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