Proof of Binomial Identity: Proving SUM(nCk)*2^k=(3^n+(-1)^n)/2

In summary, the conversation is about proving the equality SUM(nCk)*2^k=(3^n+(-1)^n)/2 for all positive integers n, with the restriction that k must be even. The suggestion is to use the binomial theorem for both (1 + 2)^n and (1 - 2)^n to come up with a solution.
  • #1
proptrader
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0

Homework Statement


Prove that for all positive integers n, the equality holds:
SUM(nCk)*2^k=(3^n+(-1)^n)/2
Note: The sum goes from k=0 to n. AND k has to be even.


Homework Equations


Binomial Theorem


The Attempt at a Solution


I know that if we use the binomial theorem for x=2 and y=1, we would get
(2+1)^n=SUM(nCk)*2^k , with no restriction for k being even. I wonder how to proceed.
Thanks.
 
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  • #2
Hint: Your idea looks like a good start. You have done (writing it in the other order) the expansion of (1 + 2)n.

Look at the same thing for (1 - 2)n and see if that gives you any ideas.
 

FAQ: Proof of Binomial Identity: Proving SUM(nCk)*2^k=(3^n+(-1)^n)/2

What is the binomial identity?

The binomial identity is a mathematical formula that relates the coefficients of a binomial expansion to the powers of the binomial terms. It is often written as SUM(nCk)*2^k=(3^n+(-1)^n)/2, where n is a positive integer and k ranges from 0 to n.

How is the proof of the binomial identity done?

The proof of the binomial identity is done using mathematical induction. This method involves proving that the formula holds true for a base case (usually n=0 or n=1) and then assuming that it holds true for a particular value of n and using that to prove that it holds true for the next value of n. This process is repeated until it is proven that the formula holds true for all values of n.

Why is the binomial identity important?

The binomial identity is important in many areas of mathematics, including probability, combinatorics, and algebra. It allows for the simplification of complicated expressions involving binomial coefficients, and it also has applications in areas such as calculus and number theory.

What are some real-life applications of the binomial identity?

The binomial identity has many real-life applications, such as in calculating the probabilities of events in coin tossing or card games. It is also used in the expansion of polynomials, which has applications in areas such as engineering and physics. Additionally, the binomial identity is used in computer science, particularly in algorithms for searching and sorting.

Are there any variations of the binomial identity?

Yes, there are several variations of the binomial identity, such as the generalized binomial theorem, which allows for the expansion of binomials with non-integer powers. There are also identities involving higher powers of the binomial terms, such as the multinomial theorem. These variations have their own proofs and applications in different areas of mathematics.

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