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Jan
27
comment Some hints for “If a prime $p = n^2+5$, then $p\equiv 1\mod 10$ or $p\equiv 9\mod 10$”
"only hints, no solution please"
Jan
24
awarded  Necromancer
Jan
13
comment What is the function of provided dataset?
How do you know it holds for all $k\in\mathbb{N}$?
Jan
13
comment Let $M = \frac{1}{2}(A + {A^T})$ be real symmetric nonnegative matrix. Why does $\rho (A) \le {\lambda _{\max }}(M)$?
What is $\rho(A)$?
Jan
13
revised Distribution random variable $W=\sum_{k=1}^{\infty}X_k/2^k$
edited title, fixed typo and improved formatting
Jan
11
comment How to proof card p(a) = card p(b)?
Are you assuming that $a$ and $b$ are finite sets?
Dec
23
revised Partitions of the odd integers
improved formatting
Dec
12
comment What is the rule of $1.96$ for estimating confidence intervals?
Fair enough. I forgot to mention that it would only be an approximation. And as you point out, it can be a poor one. Another example is binomial data with probability of success very close to zero or one.
Dec
12
comment What does 'mod' stand for in this ODE book?
If you are referring to page 19 (first edition), the next paragraph gives some information...
Dec
12
comment What is the rule of $1.96$ for estimating confidence intervals?
By the central limit theorem, you don't even need to assume normal random variables; you only need finite variance.
Dec
9
comment Closed form for $\sum_{n=0}^{\infty} \binom{n+k}{k} x^n$
I can't give you a proof, but I think you should look into Generating functions
Dec
5
comment Proving that $\mathbb{Q}(x_{1}, \sqrt{D})$ is the splitting field of all irreducible cubic polynomials in $\mathbb{Q}[x]$
Sorry, I meant $g(x_1) \in \mathbb{Q}(x_1)$
Dec
5
comment Proving that $\mathbb{Q}(x_{1}, \sqrt{D})$ is the splitting field of all irreducible cubic polynomials in $\mathbb{Q}[x]$
$g(x_1)$ is in $\mathbb{Q}$
Dec
5
comment What are the distinct cyclic subgroups of order 12 in $\mathbb{Z}_6 \times \mathbb{Z}_{10}^\times$?
I fixed the formatting of the title, but please make sure this is really what you mean. And also, could you define $U(10)$? I don't think it's standard notation...
Dec
5
revised What are the distinct cyclic subgroups of order 12 in $\mathbb{Z}_6 \times \mathbb{Z}_{10}^\times$?
fixed formatting in title
Dec
5
answered The intervals $[-1,1)$ and $(-1,1)$ are not homeomorphic
Dec
5
comment Complex numbers like a factor ring $\mathbb{C} = \mathbb{R}[t]/(t^2 + 1)\mathbb{R}[t]$
@XuqiangQin I think you can post this as an answer.
Dec
5
comment how to find the distribution of $Z=X_1/X_2$?
The expectation of a ratio is not equal to the ratio of the expectations... And in any case, the expectation alone is not enough to determine the distribution. Otherwise, normal random variables with the same mean but different variances would be equal in distribution, which is clearly absurd.
Dec
5
answered Definition of direct sum
Dec
4
comment Finite dimensional normed space
Your question should be self-contained. Please remove the link and write the equation as part of your question.