Combinations and Permutations Question

  • Thread starter snaidu228
  • Start date
  • #1
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Homework Statement



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?

Homework Equations



Binomial Expansion


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)?
 

Answers and Replies

  • #2
tiny-tim
Science Advisor
Homework Helper
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Hi snaidu228! :smile:

(try using the X2 tag just above the Reply box :wink:)
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?

Yes, that's it (except, of course, you only need the one term that has x43). :wink:

(and similarly for (2))
 
  • #3
9
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Thank you very much!
 

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