Summation with Binomial Expansion

AI Thread Summary
The discussion centers on proving the relationship involving sums of binomial coefficients. A user seeks assistance with the equation involving binomial sums and expresses difficulty in solving it both through Mathematica and by hand. Another participant points out potential issues with the original formulation, specifically that the term k-2i can be negative for certain values of i, which would invalidate the binomial coefficient. They clarify the correct definition of the binomial coefficient and emphasize that when k-2i is negative, the value should be zero. The conversation highlights the need for careful consideration of the conditions under which the binomial coefficients are defined.
Jake1802
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Homework Statement


How can i prove this relationship
\sum _{i=0}^k \text{Binomial}[n+1,k-2i] - \sum _{i=0}^k \text{Binomial}[n,k-2i]=\sum _{i=0}^k \text{Binomial}[n,k-1-2i]

Homework Equations


Binomial (n,k)=n^k/k!

The Attempt at a Solution



I attempted subbing into mathyematica but this didn't work so i attempted by hand and got completely lost. Any helpful comments would be helpful.
Result from Mathematica
-Binomial[n, -1 + k] HypergeometricPFQ[{1, 1/2 - k/2,
1 - k/2}, {1 - k/2 + n/2, 3/2 - k/2 + n/2}, 1] -
Binomial[n,
k] HypergeometricPFQ[{1, 1/2 - k/2, -(k/2)}, {1/2 - k/2 + n/2,
1 - k/2 + n/2}, 1] +
Binomial[1 + n,
k] HypergeometricPFQ[{1, 1/2 - k/2, -(k/2)}, {1 - k/2 + n/2,
3/2 - k/2 + n/2}, 1]
 
Last edited:
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Fixed your LaTex. Is this the relation you're supposed to prove?

\sum_{i=0}^k \begin{pmatrix}n+1\\k-2i\end{pmatrix} - \sum_{i=0}^k \begin{pmatrix}n\\k-2i\end{pmatrix}=\sum_{i=0}^k \begin{pmatrix}n\\k-1-2i\end{pmatrix}

I don't think it's correct because k-2i<0 for some values of i in the summation.

Binomial (n,k)=n^k/k!
That's not right. It should be

\begin{pmatrix}n\\k\end{pmatrix}=\frac{n!}{k!(n-k)!}
 
but when k-2i<0 the value will be zero
 

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