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Jan
24
reviewed Close matrix transformation help
Jan
23
reviewed Close simplify the equation
Jan
23
reviewed Close In a group of order 21, every normal subgroup is cyclic
Jan
23
reviewed Close Separable spaces and functions that separate points
Jan
22
reviewed Close Advance mathematics but not basic mathematics?
Jan
22
comment Curious Binomial Coefficient Identity
it's a (yet another) form of Vandermonde's identity
Jan
20
reviewed Close Convergence of a series uniformly
Jan
20
reviewed Close How to understand the regular cardinal?
Jan
20
reviewed Close 2-D definite Integral
Jan
20
reviewed Approve mantel theorem bipartite graphs, two triangles share an edge
Jan
19
reviewed Close I need help to evaluate this definite integral.
Jan
19
reviewed Close Graphing Quadratic Function Describing a Parabolic Arch
Jan
19
reviewed Close Solve 10 base logarithms
Jan
19
reviewed Close Proof, that helical surface is a submainfold
Jan
19
reviewed Close Forming equations for exponential growth/decay questions
Jan
19
reviewed Close Determinant of a matrix equality
Jan
19
reviewed Close Do you know any example borel algebra?
Jan
19
comment Binomial Identity $\sum\binom{2n+1}{2k+1}\binom{m+k}{2n} = \binom{2m}{2n}$
see also math.stackexchange.com/q/1107465 for a bijective proof of an equivalent identity
Jan
19
comment Showing ${n + a - 1 \choose a - 1} = \sum_{k = 0}^{\left\lfloor n/2 \right\rfloor} {a \choose n-2k}{k+a-1 \choose a-1}$
come to think of it, substituting $a\to 2n+1$, $n\to 2m-2n$ (and $k\to m-2n+k$) one can see that these two identities are equivalent
Jan
19
reviewed Close Probability (Please see picture below)