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Kryna
Oct31-09, 11:36 AM
1. The problem statement, all variables and given/known data

Prove \frac{a^{n+1}}{b+c}+\frac{b^{n+1}}{a+c}+\frac{c^{n +1}}{a+b}=(\frac{a^{n}}{b+c}+\frac{b^{n}}{a+c}+\fr ac{c^{n}}{a+b})*\sqrt[n]{\frac{a^{n}+b^{n}+c^{n}}{3}}
if n>=1 and a,b,c \in\textsl{R}_{+}

2. Relevant equations



3. The attempt at a solution
I tried prove it i some ways but i think any of it don't approach me to solution. I need a clue, don't give me solution.

PS sorry for my english

Mark44
Oct31-09, 12:22 PM
Clue: mathematical induction

Kryna
Oct31-09, 12:26 PM
Mathematical Induction is a method of proving a series of mathematical statement labelled by natural numbers

Mark44
Oct31-09, 12:49 PM
Right, and aren't your values of n natural numbers? There is no such restriction on a, b, and c.

Kryna
Oct31-09, 12:57 PM
I get

a^{2}+b^{2}+c^{2}\geq ab+bc+ac for n=1
is it true?
what is next step(i never used mathematical induction before)

if i do it for n=2 it will be proved?

Mark44
Oct31-09, 01:21 PM
For n = 1 you have to show that
\frac{a^{2}}{b+c}+\frac{b^{2}}{a+c}+\frac{c^{2}}{a +b}=(\frac{a^{1}}{b+c}+\frac{b^{1}}{a+c}+\frac{c^{ 1}}{a+b})*\frac{a^{1}+b^{1}+c^{1}}{3}

It is not sufficient to quit after showing that the original statement is true for n = 2.

In mathematical induction, you assume that the statement is true for n = k, and use that to show that the statement is also true for n = k + 1.

Kryna
Oct31-09, 04:21 PM
Thanks for helping me.