Understanding Binomial Coefficients: Finding the r-th term formula

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SUMMARY

The discussion centers on the formula for the r-th term in the binomial expansion, specifically T_n+1 = C_n^r a^{n-r} b^r, which represents the (r+1)-th term. The user seeks clarification on the variables a and b and how to derive the r-th term from the general term formula. The binomial expansion is referenced as (a+b)^{n} = ∑_{k=0}^{n} C_{n}^{k} a^{n-k} b^{k}, indicating the relationship between coefficients and terms. The user has constructed a Pascal triangle up to the 10th row to aid in understanding.

PREREQUISITES
  • Understanding of binomial coefficients, specifically C_n^r
  • Familiarity with binomial expansion and its properties
  • Basic knowledge of algebraic expressions and terms
  • Experience with Pascal's triangle and its application in combinatorics
NEXT STEPS
  • Research the derivation of the r-th term in binomial expansions
  • Explore the properties of binomial coefficients and their applications
  • Study examples of binomial expansions with different values of a and b
  • Learn how to construct and utilize Pascal's triangle for combinatorial problems
USEFUL FOR

Students studying IB mathematics, particularly those focusing on combinatorics and binomial expansions, as well as educators seeking to explain these concepts effectively.

gschjetne
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I'm working on an IB mathematics portfolio, and here's a problem I don't understand:
The formula for the general term is
[tex] T_n+1=C_n^r a^{n-r} b^r[/tex]
Verify this formula by examples. This is the formula for the [itex](r+1)[/itex]-th term.
What would the formula for the [itex]r[/itex]-th term be?
It's not specified what [itex]a[/itex] and [itex]b[/itex] is supposed to represent. That's where I need some explanation.
I already made a nice Pascal triangle all the way to the 10th row.
All help is appreciated.
 
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My guess is that it comes from the expansion:

[tex](a+b)^{n}=\sum_{k=0}^{n}C_{n}^{k} a^{n-k}b^{k}[/tex]

Daniel.

PS.Can u handle the [itex](n-1)[/itex] term part??
 
Thanks, I'll give it a try
 

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