Proving the given quadratic form is chi-squared $k$
12485
Distribution of a quadratic form, non-central chi-squared distribution
71564
Combinatorial proof of identity involving central binomial coefficients
9522
Proving $k \binom{n}{k} = n \binom{n-1}{k-1}$
146762
Closed form for $\sum_{k=0}^{n} \binom{n}{k}\frac{(-1)^k}{(k+1)^2}$
72841
Proof that if $Z$ is standard normal, then $Z^2$ is distributed Chi-Square (1).
113321
Hint proving this $\sum_{k=0}^{n}\binom{2n}{k}k=n2^{2n-1}$
134439
Proving function is $C^k$
136580
Proving $\sum_{k=0}^n\binom{2n}{2k} = 2^{2n-1}$
87320
Proving identities like $\sum_{k=1}^nk{n\choose k}^2=n{2n-1\choose n}$ combinatorially
116461
Prove the identity $\sum_{k=0}^{n}(-1)^{k}\binom{n}{k}=0$ using a combinatorial interpretation of the positive and negative terms
489
How to take the gradient of the quadratic form?
33104
Combinatorial Proof with Summation Identity
87479
Closed form for $\sum_{k=0}^{n-p}\binom{n}{k}\binom{n}{p+k}$
116491
Closed form for $\sum_{k=0}^{m} {\binom {m}{k}} a^{k} (b+ck)^N$
139711
prove this inequality with $\sum\limits_\text{cyc}\sqrt{1-xy}\ge 2$
132125
finding if two binary quadratic forms represent the same integers
46308
Simultaneous diagonlisation of two quadratic forms, one of which is positive definite