$n$ is a natural number. for every positive real numbers $x_{1},x_{2},...,x_{n+1}$ such that $x_{1}x_{2}...x_{n+1}=1$ prove that: $\sqrt[x_{1}]{n}+...+\sqrt[x_{n+1}]{n} \geq n^{\sqrt[n]{x_{1}}}+...+n^{\sqrt[n]{x_{n+1}}}$
Problem
Source: iran tst 2014 first exam
Tags: inequalities, function, inequalities unsolved, n-variable inequality
15.04.2014 19:52
17.04.2014 13:23
it is easy problem by http://www.artofproblemsolving.com/Forum/viewtopic.php?f=55&t=113248&p=643414&hilit=smv#p643414
28.05.2014 07:11
By Karamata inequality this reduces to proving that if $a_1+...+a_{n+1}=0$ and we let $a$ be that sequence, and $-a/n$ denote the sequence $(-a_1/n)+...+(-a_{n+1}/n)=0$, we must prove $a$ majorizes $-a/n$ WLOG $a_1 \ge ... \ge a_n$. Let $X_i=a_i+...+a_{i+x-1}$ for a given $1 \le x \le n+1$, with indices mod $n+1$. Notice that, if $b_i=-a{n+2-i}/n$ then $b_1 \le ... \le b_n$ and $0 = X_1+...+X_n \le nX_1+X_{n+2-x} \Rightarrow a_1+...+a_x = X_1 \ge X_{n+2-x}/n = b_1+...+b_x$ for all $x$, so we're done.
01.06.2014 07:07
Is thwre solution by AM GM??
01.06.2014 10:31
ThisIsART wrote: Is thwre solution by AM GM?? see my post .. my solution is just AM-GM
01.06.2014 15:05
I do not understand i am sorry give complete solution please
06.06.2014 20:33
Let $f(x)=n^{e^x}$. Since $f$ is a convex function, we can use Karamata.
07.06.2014 05:07
I have not study about convex and concaf function i am sorry sir
30.07.2020 13:12
10.08.2020 21:59
Aryan-23 wrote:
Nice Solution.