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3 answers
7 votes
120 views
Pointwise convergence of sequence $(f_n)_n$ of functions to $f$ and changing limits
5 answers
5 votes
155 views
Computing $7^{13} \mod 40$
2 answers
5 votes
656 views
Compute $5!25! \mod 31$
1 answers
5 votes
5k views
5 bookmarks
Tensor product of localization is isomorphic to localization of tensor product
1 answers
4 votes
73 views
Subgroups of finitely generated group are not necessarily finitely generated (proof).
2 answers
4 votes
360 views
1 bookmarks
Restriction of homomorphism to finite index subgroup gives finite index subgroup of kernel
1 answers
4 votes
259 views
Boundary $\partial F_n$ of a free group $F_n$
1 answers
4 votes
345 views
Prove that the following map has at least $k-2$ fixed points
2 answers
4 votes
61 views
1 bookmarks
If $x = y^3$ in $\mathbb{Z} + \frac{-1 + \sqrt{-3}}{2}\mathbb{Z}$, then there is some $w \in \mathbb{Z} + \sqrt{-3}\mathbb{Z}$ such that $x = w^3$.
1 answers
4 votes
345 views
1 bookmarks
isomorphic extension fields of the $p$-adic numbers
2 answers
4 votes
428 views
Inverse image of a Noetherian module under a module morphism
3 answers
3 votes
159 views
Prove that $\sum_{k = 0}^{49}(-1)^k\binom{99}{2k} = -2^{49}$
2 answers
3 votes
3k views
1 bookmarks
Why is this function only differentiable at zero?
1 answers
3 votes
254 views
$x_n \to x \in \mathbb{R}$ and $y_n \to 0 $. What about $\frac{x_n}{y_n}$?
2 answers
3 votes
86 views
image of homomorphism contains free group, then so does domain
1 answers
3 votes
120 views
automorphism of free group $F_n$ fixing $F_{n-1}$ and image of $n$th generator
1 answers
3 votes
108 views
components of subgraph determine subgroups up to conjugacy
2 answers
3 votes
122 views
1 bookmarks
Proving that $a+b\sqrt{-3}$ is a cube if $a^2 + 3b^2 = c^3$
0 answers
3 votes
72 views
1 bookmarks
Factoring $a + b\frac{1 + \sqrt{5}}{2}$ if $a^2 + ab - b^2 = a+b$
0 answers
3 votes
134 views
1 bookmarks
showing elements in $\mathbb{Z}+\frac{1 + \sqrt{5}}{2}\mathbb{Z}$ are associated
3 answers
3 votes
131 views
1 bookmarks
Question about definition of graded ring
2 answers
3 votes
708 views
3 bookmarks
Proving $(x_1 - a_1, \ldots, x_n -a_n)$ is a maximal ideal
1 answers
3 votes
334 views
Proof about positive semi-definite matrix
3 answers
3 votes
72 views
Find all couples $(a,b) \in \mathbb{Z}^2$
4 answers
3 votes
3k views
Number of elements of order 2
2 answers
2 votes
147 views
finding smallest natural number $n$ such that $n \equiv 1023 \bmod 2015$ and $n \equiv 1302 \bmod 2016$
2 answers
2 votes
105 views
Let K be a non-abelian subgroup of dihedral group and $H = K \cap \{1, a, a^2, \ldots, a^{n-1}\}$ then the index of H in K is 2.
1 answers
2 votes
33 views
combinatorics problem: ordering people from small to large. Is my solution correct?
2 answers
2 votes
198 views
2 bookmarks
lim inf and lim sup of sequence obtained from combination of two sequences
1 answers
2 votes
175 views
Collapsing subgraph: Bogopolski's "Introduction to group theory"