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1d
comment Show the closed form of the sum $\sum_{i=0}^{n-1} i x^i$
Please do not deface your question, even if it is currently marked as duplicate.
1d
revised Show the closed form of the sum $\sum_{i=0}^{n-1} i x^i$
rolled back to a previous revision
1d
comment I need help to solve this complex question
Please do not deface your question, even if it is marked as duplicate.
1d
revised I need help to solve this complex question
rolled back to a previous revision
1d
revised Tricky Cardinality Question/Riddle
rolled back to a previous revision
1d
comment Tricky Cardinality Question/Riddle
Please do not deface your question.
1d
comment Absolute continuity of a distribution function
Got something from an answer below?
2d
comment How do I show that $0<a_n^2<a_n$ If $\sum _{n=1}^\infty a_n$ is convergent?
@alex Apart from the OP's name, how did you choose the answer you accepted?
2d
comment How do I show that $0<a_n^2<a_n$ If $\sum _{n=1}^\infty a_n$ is convergent?
Yes, $a_n>0$ for every $n$, and why would this imply that $(a_n)$ decreases to $0$?
2d
comment Proof of infinite monkey theorem.
@PeterFranek Indeed it does not matter much. math.stackexchange.com/q/17152
2d
comment Expected value of conditional expectation, discrete variable
"So it suffices to prove that $\mathbb{E}(\mathbb{E}(X|Y)) = \mathbb{E}Y$" No. You might mean $\mathbb{E}(\mathbb{E}(X|Y)) = \mathbb{E}(X)$ instead, but even that does not amount to what you are asked to prove.
2d
comment Use the persistence theory to find a set of sufficient conditions for two species competitive ODE system
"Persistence theory"? What is it?
2d
comment Show that the solution of the Cauchy problem $x(t,t_0,x_0)$, $x(t_0)=x_0$ is definite for all $t\geq t_0$.
$\le$ in the title vs $\ge$ in the text, which one to believe?
2d
comment Velocity field arrows along null clines as well as outside null clines
Q8 does not ask to sketch velocity field arrows along null clines.
2d
comment A trick and interesting math SUM
Tricky: moderately. Interesting: why exactly?
2d
comment A trick and interesting math SUM
The identity holds, Doc. You might want to check your "counterexample".
2d
comment Summation of $3^k$ from $2$ to $72$
This tragicomic play has already been played countlessly many times with you, to no avail, but here we go again: I know how to prove the result, thank you, the discussion is about the usefulness of your answer--which, at the moment, I happen to evaluate at nearly zero for the reasons in my first comment. And no, your answer is not the same as the accepted one. Not at all. That you can even pretend otherwise is a true mystery to me, @Doc.
2d
comment Proof of infinite monkey theorem.
@PeterFranek You are thinking about one monkey typing forever while the question asks about infinitely many monkeys typing the exact number of keys in the complete works of William Shakespeare, and then stopping. Which of these two situations is the most unrelated to the real world is a debatable point. But yes, Borel-Cantelli is definitely overkill.
2d
comment Random variables set representation in the sample space
Definition of what? Of A? This is in every introductory text to probability theory, I believe.
2d
comment Prove $\{s_n\}$ converges if $\{a_n = s_n + 2s_{n+1}\}$ converges.
And now, duplicates, near-duplicates, functional duplicates of the question abound.