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476160
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location Buenos Aires, Argentina
age 21
visits member for 2 years, 6 months
seen 5 hours ago

(My avatar is a piece by artist Pollock named "Number 8".)

Some interesting questions, with great answers:

  1. The so-called Axiom of Choice

  2. Real numbers and sets

  3. How discontinuous can a derivative be?

  4. Why is summation by parts important? This is one example.

  5. Amazing work


17h
revised Help to clarify inductive step for proof of $\mathbb{N_m} \rightarrow \mathbb{N}_n\Rightarrow m\le n$
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18h
answered Help to clarify inductive step for proof of $\mathbb{N_m} \rightarrow \mathbb{N}_n\Rightarrow m\le n$
18h
comment Help to clarify inductive step for proof of $\mathbb{N_m} \rightarrow \mathbb{N}_n\Rightarrow m\le n$
What do you mean by $\Bbb N_m$? $\{1,\ldots,m\}$?
1d
comment A sequence and convergence
@Kelenner In some sense, I am repeating the proof of the fact that Cesaro summation preserves sums. True.
1d
comment Invertibility of $I-AB$
@Guess I just used the word "ring" but this is entirely elementary, and simple. The formal method is "multiply $(1-yx)$ by $1+y(1-xy)^{-1}x$ and see it gives $1$".
1d
answered Invertibility of $I-AB$
1d
revised A sequence and convergence
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1d
answered A sequence and convergence
1d
revised Prove $Q_8$, the group generated by two complex matrices $A$ & $B$ (see below) is a nonabelian group of order 8.
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1d
revised if $\frac{1}{(1-x^4)(1-x^3)(1-x^2)}=\sum_{n=0}^{\infty}a_{n}x^n$,find $a_{n}$
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1d
answered if $\frac{1}{(1-x^4)(1-x^3)(1-x^2)}=\sum_{n=0}^{\infty}a_{n}x^n$,find $a_{n}$
1d
comment Surjectivity implies injectivity of finitely generated modules, localization?
@MartinBrandenburg Why'd he delete this one?
1d
comment Surjectivity implies injectivity of finitely generated modules, localization?
The idea in Eisenbud is due to a guy named Vasconcelos, I think. Note he's using Cayley Hamilton.
2d
comment How to see 4th dimension?
Drugs? ${}{}{}$
2d
revised Suppose that $V_1$ and $V_2$ are subsets of a vector space…
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2d
comment Suppose that $V_1$ and $V_2$ are subsets of a vector space…
@Eric I meant $\langle x\rangle$, $\langle y\rangle$ where $x,y$ are linearly independent.
Jul
22
comment How to find the Direct Discrete Laplace Transform of ${2n \choose n}$
Yes. You can use Google. I promise you'll find references.
Jul
22
answered How to find the Direct Discrete Laplace Transform of ${2n \choose n}$
Jul
22
answered Suppose that $V_1$ and $V_2$ are subsets of a vector space…
Jul
22
comment Maximum of $\frac{x(1-x)y(1-y)}{1-xy}$ over $[0,1] \times [0, 1]$?
Yes.${}{}{}{}{}$