State and prove a natural generalization

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Homework Help Overview

The discussion revolves around a problem requesting a natural generalization of the Arithmetic-Geometric (AG) Inequality, specifically starting from the case of three positive real numbers. Participants are tasked with interpreting the request and exploring potential generalizations.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants are questioning the meaning of "natural generalization" and whether it pertains to proving the original AG Inequality or extending it to other cases. Some suggest exploring the case for four positive real numbers and whether a similar inequality holds. Others propose that the proof might follow a specific form related to the AG Inequality.

Discussion Status

The discussion is active with various interpretations being explored. Some participants are considering the implications of extending the inequality to more than three variables, while others are contemplating the proof structure. There is no explicit consensus yet, but several productive lines of inquiry are being pursued.

Contextual Notes

Participants are navigating the constraints of the problem, including the specific case of three numbers and the potential for generalization to n numbers. The original statement and its implications are under examination, with some uncertainty about the requirements for the proof.

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Homework Statement


State and prove a natural generalization of "prove that for any three positive real numbers x1, x2, x3, x1/x2 + x2/x3 + x3/x1 \geq 3.


Homework Equations


AG Inequality is used in subproof (x1/x2 + x2/x3 + x3/x1 \geq 3)


The Attempt at a Solution


I don't know what the book means exactly by a "natural generalization". Does it want me to prove the original AG Inequality or relate it somehow to this specific instance of the AG Inequality?
 
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What's special about the statement being true for 3 numbers? Is it true that for any 4 positive real numbers x_1, x_2, x_3, x_4
<br /> \frac{x_1}{x_2}+\frac{x_2}{x_3}+\frac{x_3}{x_4}+ \frac{x_4}{x_1} \geq 4 \; ?<br />
Can you generalize?
 
So it's asking for a proof of the form (x1+x2+...+xn)/n \geq \sqrt[n]{x<sub>1</sub>x<sub>2</sub>...x<sub>n</sub>} . So, I should prove the Arithmetic-Geometric Mean Inequality?
 
Last edited:
major_maths said:
So it's asking for a proof of the form (x1+x2+...+xn)/n \geq \sqrt[n]{x<sub>1</sub>x<sub>2</sub>...x<sub>n</sub>} . So, I should prove the Arithmetic-Geometric Mean Inequality?

If by "of the form," you mean for n positive real numbers, then yes. I'm guessing the same trick you used for the n=3 case will work in general. If not, proof by induction might work.
 

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