Inequality(open ended)[made by shanzeed anwar]

For discussing Olympiad Level Number Theory problems
User avatar
nafistiham
Posts:829
Joined:Mon Oct 17, 2011 3:56 pm
Location:24.758613,90.400161
Contact:
Inequality(open ended)[made by shanzeed anwar]

Unread post by nafistiham » Thu Jan 12, 2012 8:28 pm

posting on request.

Let $a_1,a_2,a_3,.....,a_n$ are positive real numbers.
prove or disprove it,
if,
\[a_1+a_2+a_3+.....+a_n=n\]
then,
\[\sum_{cyclic}^{} \frac{a_1}{1+a_2^2}\geq \frac {n}{2}\]

Example:
$\sum_{cyclic}^{} \frac{a}{1+b^2}$ for $a,b,c$ is equal to
\[\frac{a}{1+b^2}+\frac{b}{1+c^2}+\frac{c}{1+a^2}\]
\[\sum_{k=0}^{n-1}e^{\frac{2 \pi i k}{n}}=0\]
Using $L^AT_EX$ and following the rules of the forum are very easy but really important, too.Please co-operate.
Introduction:
Nafis Tiham
CSE Dept. SUST -HSC 14'
http://www.facebook.com/nafistiham
nafistiham@gmail

User avatar
SANZEED
Posts:550
Joined:Wed Dec 28, 2011 6:45 pm
Location:Mymensingh, Bangladesh

Re: Inequality(open ended)[made by shanzeed anwar]

Unread post by SANZEED » Tue Jan 17, 2012 6:32 pm

It's open ended because the equality is only my conjecture.
$\color{blue}{\textit{To}} \color{red}{\textit{ problems }} \color{blue}{\textit{I am encountering with-}} \color{green}{\textit{AVADA KEDAVRA!}}$

User avatar
Phlembac Adib Hasan
Posts:1016
Joined:Tue Nov 22, 2011 7:49 pm
Location:127.0.0.1
Contact:

Re: Inequality(open ended)[made by shanzeed anwar]

Unread post by Phlembac Adib Hasan » Wed Jan 18, 2012 2:25 pm

I think it may be not true for all $n$s.Re-arrangement inequality gives me such a result that may not be true for large $n$s.It's very ugly so I'm not posting it here.Now I 'll try to find out such a case that does not follow this inequality.
Welcome to BdMO Online Forum. Check out Forum Guides & Rules

Post Reply