Boris Novikov

Member for 10 years, 9 months
Last seen more than 9 years ago

funcan.univer.kharkov.ua/…
Ukraine

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abstract-algebra

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45

Prove that the additive group $ℚ$ is not isomorphic with the multiplicative group $ℚ^*$.

Mar 19, 2013

43

Why is $\frac{987654321}{123456789} = 8.0000000729?!$

May 19, 2013

24

if $ab=cd$ then $a+b+c+d $ is composite

May 6, 2013

15

Prove that $(G, \circ)$ is a group if $a\circ x = b$ and $x\circ a = b$ have unique solutions

Mar 30, 2013

15

Good math bed-time stories for children?

Nov 7, 2013

Questions

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4

Does someone know other examples of $K$-semigroups?

Apr 25, 2013

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abstract-algebra

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linear-algebra

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Reputation

+10

Prove that if $AB$ is invertible then $B$ is invertible.

+10

$\left(\sum\limits_{i=1}^N (a_i+b_i)^2\right)^2 \stackrel{?}{=} \sum\limits_{i=1}^N (a_i+b_i)^4 $ where $a_i,b_i \in \mathbb{R}$

+10

Ring theory reference books

+10

Let $G$ be abelian, $H$ and $K$ subgroups of orders $n$, $m$. Then G has subgroup of order $\operatorname{lcm}(n,m)$.

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