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visits member for 2 years, 10 months
seen Aug 4 at 20:30

Jan
23
revised Find $C$, if $A=CBC$, where $A$,$B$,$C$ are symmetric matrices.
added 21 characters in body
Jan
23
asked Find $C$, if $A=CBC$, where $A$,$B$,$C$ are symmetric matrices.
Sep
21
awarded  Custodian
Aug
15
comment Is addition more fundamental than subtraction?
@Ben Millwood good point !!! :) ps. I cant edit my comments, and there are some misstakes
Aug
14
comment Is addition more fundamental than subtraction?
now use triangle unequality...
Aug
14
comment Is addition more fundamental than subtraction?
@Joachim writes that subtraction is not even an operation, that is because subraction is something more general, now we could argue if more general means more fundamental :D And that is fundamental reason way my above translation is possible ;) (But there are some hiden assumptions in my post;)
Aug
14
comment Is addition more fundamental than subtraction?
We start with two statements "0", "a+b" and "a-b" which we understand and want to translate into one another. a+b=a-(0-b), a-b=a+(-b) addition is defined using only subtraction and subtraction isnt defined using anly addition, because to define -b, in terms of "a+b" and "a-b" statements we have to write -b=0-b, so writing a-b=a+(-b) isnt very fundamental ti should be a+(0-b). Both equation needs definition of 0.So subtraction is more fundamental
Aug
8
accepted What is the sum of $\sum\limits_{i=1}^{n}i^k p^i$?
Aug
8
asked What is the sum of $\sum\limits_{i=1}^{n}i^k p^i$?
Aug
8
revised What is the sum of $\sum\limits_{i=1}^{n}ip^i$?
added 128 characters in body
Aug
8
accepted What is the sum of $\sum\limits_{i=1}^{n}ip^i$?
Aug
8
asked What is the sum of $\sum\limits_{i=1}^{n}ip^i$?
Jul
20
accepted What is $f(t)=X_{t+1}$, if $X_{t+1}=(1-p)(1-X_{t})+pX_{t}$ and $X_{0},p \in [0,1]$?
Jul
20
asked What is $f(t)=X_{t+1}$, if $X_{t+1}=(1-p)(1-X_{t})+pX_{t}$ and $X_{0},p \in [0,1]$?
May
21
accepted What is the number of functions $f : A\rightarrow A, \forall_{x\in{A}} f(f(x))=x$, set $A$ have $n$ distinct elements.
May
17
awarded  Commentator
May
17
comment What is the number of functions $f : A\rightarrow A, \forall_{x\in{A}} f(f(x))=x$, set $A$ have $n$ distinct elements.
yes, it's the essence of my question
May
17
asked What is the number of functions $f : A\rightarrow A, \forall_{x\in{A}} f(f(x))=x$, set $A$ have $n$ distinct elements.
May
14
comment Is $M=\{(x,y)\in (0,\infty )\times\mathbb{R} : y=\sin(\frac{1}{x}) \}$ a closed set in space $((0,\infty )\times\mathbb{R} ,\rho_{e})$?
I like your answer also, but Cameron Buie was first.
May
14
accepted Is $M=\{(x,y)\in (0,\infty )\times\mathbb{R} : y=\sin(\frac{1}{x}) \}$ a closed set in space $((0,\infty )\times\mathbb{R} ,\rho_{e})$?