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]
 
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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
 
I tried to combine those 2 formulas but it didn't work. I tried using another case where there are 2 red balls and 2 blue balls only so when combining the formula I got ##\frac{(4-1)!}{2!2!}=\frac{3}{2}## which does not make sense. Is there any formula to calculate cyclic permutation of identical objects or I have to do it by listing all the possibilities? Thanks
Since ##px^9+q## is the factor, then ##x^9=\frac{-q}{p}## will be one of the roots. Let ##f(x)=27x^{18}+bx^9+70##, then: $$27\left(\frac{-q}{p}\right)^2+b\left(\frac{-q}{p}\right)+70=0$$ $$b=27 \frac{q}{p}+70 \frac{p}{q}$$ $$b=\frac{27q^2+70p^2}{pq}$$ From this expression, it looks like there is no greatest value of ##b## because increasing the value of ##p## and ##q## will also increase the value of ##b##. How to find the greatest value of ##b##? Thanks

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