3,699 reputation
1418
bio website none
location Sissa, Italy
age 26
visits member for 2 years, 7 months
seen Apr 15 at 8:11

I'm a poor little math student :)


Aug
27
awarded  Yearling
Feb
6
comment Proving ${(n+2)!}< \left(n(\sqrt{2}-1)+\sqrt{2}\right)^{n+2}$
For zero it is false :)
Feb
4
revised Prove that f is differentiable in $\mathbb{R}$
edited title
Feb
4
comment Find all the functions which satisfy a given functional equation
@DejanGovc Thanks for pointing it out. Indeed I was wrong. now It should be fixed and luckily It was just me to be too lazy and always looking for a shortcut :D thanks again
Feb
4
revised Find all the functions which satisfy a given functional equation
added 62 characters in body
Feb
4
comment Find all the functions which satisfy a given functional equation
I substitute $f(x)-1\mapsto f(x)$. Does it convince you?
Feb
4
revised Find all the functions which satisfy a given functional equation
added 58 characters in body
Feb
4
answered Find all the functions which satisfy a given functional equation
Feb
2
revised Find all the functions which satisfy a given functional equation
edited title
Feb
2
comment A problem about the additivity of exterior measure.
right.. You do not have to worry then in this case that something might go wrong. The fact holds in much more generality, in your case it's a special case let's say.
Feb
1
answered Inequality of real numbers
Feb
1
comment A problem about the additivity of exterior measure.
That K is Well contained in E, That is $\bar K \subset E $
Jan
31
comment Show $d(x,y)=\sup|\alpha^k-\beta^k|$ satisfies triangle inequality
If it is so the first inequality comes from the fact that in general, if you have two sequences, say $a_k, b_k$, then $\sup_k a_k+\sup_k b_k\geq \sup_k (a_k+b_k)$. For the other, notice that by the triangle inequality you are majorizing termwise. So it's ok.
Jan
31
comment Show $d(x,y)=\sup|\alpha^k-\beta^k|$ satisfies triangle inequality
did I interpret right?
Jan
31
revised Show $d(x,y)=\sup|\alpha^k-\beta^k|$ satisfies triangle inequality
added 43 characters in body
Jan
31
answered A problem about the additivity of exterior measure.
Jan
29
comment Given $F:X \to X$ on $X$:Hilbert space satisfying some properties, prove that $F$ is surjective.
Yes Indeed you are right. In finite dimensional spaces the usual topological degree suffices. If you want a result also for Infinite dimensional spaces you have to use the more sofisticated Leray Schauder degree.
Jan
29
awarded  Fanatic
Jan
28
revised Given $F:X \to X$ on $X$:Hilbert space satisfying some properties, prove that $F$ is surjective.
added 6 characters in body
Jan
28
comment Given $F:X \to X$ on $X$:Hilbert space satisfying some properties, prove that $F$ is surjective.
As for your first point. Well... If you don't even know that it is linear there is no reasonable statement you can apply to your problem. I implicitly assumed the operator to be linear because otherwise I wouldn't know even where to start. For the second point.. yes, it is not a consequence of the fixed point theorem. I will look for the reference though