Use of binomial theorem in a sum of binomial coefficients?

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SUMMARY

The discussion focuses on utilizing the binomial theorem to find sums involving binomial coefficients, specifically the series S={n\choose 1}-3{n\choose 3}+9{n\choose 5}-. The participants clarify how to express this sum using summation notation and the binomial theorem, defined by the equation (a+b)^n=\sum\limits_{k=0}^{n}{n\choose k}a^{n-k}b^k. A solution is proposed where S_n is represented as a piecewise function based on whether n is even or odd, with suggestions to use computer algebra systems like Maple or Mathematica for further analysis.

PREREQUISITES
  • Understanding of binomial coefficients and their notation, {n\choose k}
  • Familiarity with the binomial theorem and its formula, (a+b)^n=\sum\limits_{k=0}^{n}{n\choose k}a^{n-k}b^k
  • Basic knowledge of summation notation, \sum\limits
  • Experience with computer algebra systems such as Maple or Mathematica
NEXT STEPS
  • Explore advanced applications of the binomial theorem in combinatorial problems
  • Learn how to manipulate binomial coefficients in summation expressions
  • Investigate the capabilities of Maple and Mathematica for solving complex algebraic sums
  • Study the use of Wolfram Alpha for evaluating binomial coefficient sums
USEFUL FOR

Students studying combinatorics, mathematicians working with binomial coefficients, and anyone seeking to deepen their understanding of the binomial theorem and its applications in algebraic sums.

gruba
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Homework Statement


How to use binomial theorem for finding sums with binomial coefficients?
Example: S={n\choose 1}-3{n\choose 3}+9{n\choose 5}-...

How to represent this sum using \sum\limits notation (with binomial theorem)?

Homework Equations


(a+b)^n=\sum\limits_{k=0}^{n}{n\choose k}a^{n-k}b^k

The Attempt at a Solution


I am completely stuck on this types of problems (modify binomial formula so that it gives some arbitrary sum). Could someone please explain this example?
 
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gruba said:

Homework Statement


How to use binomial theorem for finding sums with binomial coefficients?
Example: S={n\choose 1}-3{n\choose 3}+9{n\choose 5}-...

How to represent this sum using \sum\limits notation (with binomial theorem)?

Homework Equations


(a+b)^n=\sum\limits_{k=0}^{n}{n\choose k}a^{n-k}b^k

The Attempt at a Solution


I am completely stuck on this types of problems (modify binomial formula so that it gives some arbitrary sum). Could someone please explain this example?

Are the coefficients supposed to be ##(-3)^0, (-3)^1, (-3)^2, \ldots##? If so, what is preventing you from using the formula you wrote under heading 2?
gruba said:

Homework Statement


How to use binomial theorem for finding sums with binomial coefficients?
Example: S={n\choose 1}-3{n\choose 3}+9{n\choose 5}-...

How to represent this sum using \sum\limits notation (with binomial theorem)?

Homework Equations


(a+b)^n=\sum\limits_{k=0}^{n}{n\choose k}a^{n-k}b^k

The Attempt at a Solution


I am completely stuck on this types of problems (modify binomial formula so that it gives some arbitrary sum). Could someone please explain this example?

I assume you mean
S_n = \begin{cases}<br /> \displaystyle \sum_{k=0}^{m-1} (-3)^k {2m \choose 2k+1}, &amp; n = 2m \\<br /> \displaystyle \sum_{k=0}^m (-3)^k {2m+1 \choose 2k+1}, &amp; n = 2m + 1<br /> \end{cases}<br />
If so, these are not particularly easy to determine. A computer algebra package such as Maple or Mathematica can determine the answers. You can also submit them to the free on-line package Wolfram Alpha.
 
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