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2d
comment Function with zero description
What is a nice function? What delta are you talking about? Kronecker's Delta?
Dec
22
comment What happens from $\displaystyle (1+(x+x^2))^n$ to $\displaystyle \sum_k {n \choose k} (x+x^2)^n$?
Oh, thanks. Now what's unclear to me is the creation of: $$\sum_j {k \choose j} x^j$$ I don't understand why he's using $k$ nor why he used $j$.
Dec
22
comment What happens from $\displaystyle (1+(x+x^2))^n$ to $\displaystyle \sum_k {n \choose k} (x+x^2)^n$?
I've been able to reach to: $$\sum_k{n \choose k}1^k(x+x^2)^{n-k}$$ But I don't understand how he gets to the next step. Also, in this step, he writes: $$\sum_k{n \choose k}1^k(x+x^2)^{k}$$ I don't understand why he omitted the $n$ in $n-k$.
Dec
21
accepted What happens from $\displaystyle (1+(x+x^2))^n$ to $\displaystyle \sum_k {n \choose k} (x+x^2)^n$?
Dec
21
reviewed Approve prove that $O^{\pi}(G) \leq K$ .
Dec
21
asked What happens from $\displaystyle (1+(x+x^2))^n$ to $\displaystyle \sum_k {n \choose k} (x+x^2)^n$?
Dec
21
accepted What's the meaning of “reuse space”?
Dec
20
comment Text suggestion for linear algebra and geometry
@5space People in MSE are not reading the body of the question anymore. They read only what you put in the title. I've noticed this a lot in my questions.
Dec
20
comment Show that the number of subsets of $S_1 \cup \dots \cup S_t$ that contain at most one element from each $S_i$ is $(a_1 + 1)(a_2 + 1) \dots (a_t + 1)$.
But is it possible to derive some reasoning from the generating functions?
Dec
20
comment Show that the number of subsets of $S_1 \cup \dots \cup S_t$ that contain at most one element from each $S_i$ is $(a_1 + 1)(a_2 + 1) \dots (a_t + 1)$.
But is it possible to derive some reasoning from the generating functions?
Dec
20
asked Show that the number of subsets of $S_1 \cup \dots \cup S_t$ that contain at most one element from each $S_i$ is $(a_1 + 1)(a_2 + 1) \dots (a_t + 1)$.
Dec
19
awarded  Constituent
Dec
19
comment How to solve this kind of problem?
@brick Anything, I guess. I'm not sure if the operations have prority. I just found this randomly on the internet, there were no instructions.
Dec
19
revised How to solve this kind of problem?
added 174 characters in body; edited tags
Dec
19
asked How to solve this kind of problem?
Dec
18
comment Continuity of Modified Hom Functor
My eyes switched the letters in my first read. I read Mom Functor.
Dec
18
asked Could you expand a little on this proof or Floyd-Warshall Algorithm?
Dec
18
awarded  Famous Question
Dec
18
asked What's the meaning of “reuse space”?
Dec
17
comment Blackboard bold, Bold, Fraktur, and Reserved Variable.
Probably because it's easier to type. **R** is easier than $\mathbb{R}$.