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Aug
14
awarded  Enlightened
Aug
14
awarded  Nice Answer
Aug
7
awarded  Nice Question
Aug
5
comment When a complex matrix is similar to a real matrix?
It's not true in general: for $1\times 1$-matrices, similar matrices are equal. Hence $(i)$ cannot be similar to a real matrix.
Aug
4
comment Show that a subspace of l2 is not complete
The limit of the rest sums converging to zero is by definition the same as the series converging. For this specific series, you can show convergence using the usual criteria for series convergence, like the quotient criterion, or you can simply compute the rest sums explicitly.
Aug
4
comment Show that a subspace of l2 is not complete
Yes, it's correct. I could however imagine correctors that would like to see an argument supporting that the limit in the end is zero. This of course follows directly from the definition of convergent series.
Jul
28
awarded  Yearling
Jul
22
comment Determined or not?
You could ask the same question about $\dfrac{x}{x}$.
Jul
16
revised How many ways can 8 people be seated in a row?
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Jul
12
revised Why locally compact hausdorff space
added 85 characters in body
Jul
12
comment Why locally compact hausdorff space
Thanks, @DanielFischer, I've added some remarks in a vein similar to your comment.
Jul
12
revised Why locally compact hausdorff space
added 444 characters in body
Jul
12
answered Why locally compact hausdorff space
Jul
12
comment Why locally compact hausdorff space
@Crostul: why would it not be a Banach space?
Jul
12
comment Why locally compact hausdorff space
@PeterFranek: We are looking at function from $\mathbb Q$ to, say, $\mathbb C$ not function to $\mathbb Q$.
Jul
8
comment Relative cohomology versus cohomology.
Did you mean $S/X$ instead of $S\setminus X$?
Jul
2
awarded  Curious
Jul
2
awarded  Inquisitive
Jun
27
awarded  Nice Answer
Jun
18
awarded  Nice Answer