Difference between revisions of "AM-GM Inequality"
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== Generalizations == | == Generalizations == | ||
− | + | The AM-GM Inequality has been generalized into several other inequalities, which either add weights or relate more means in the inequality. | |
=== Weighted AM-GM Inequality === | === Weighted AM-GM Inequality === | ||
− | + | The '''Weighted AM-GM Inequality''' relates the [[Weighted average | weighted]] arithmetic and geometric means. It states that for any list of weights <math>\omega_1, \omega_2, \ldots, \omega_n \geq 0</math> such that <math>\omega_1 + \omega_2 + \cdots + \omega_n = \omega</math>, <cmath>\frac{\omega_1 x_1 + \omega_2 x_2 + \cdots + \omega_n x_n}{\omega} \geq \sqrt[\omega]{x_1^{\omega_1} x_2^{\omega_2} \cdots x_n^{\omega_n}},</cmath> with equality if and only if <math>x_1 = x_2 = \cdots = x_n</math>. When <math>\omega_1 = \omega_2 = \cdots = \omega_n = 1/n</math>, the weighted form is reduced to the AM-GM Inequality. Several proofs of the Weighted AM-GM Inequality can be found in the [[proofs of AM-GM]] article. | |
=== Mean Inequality Chain === | === Mean Inequality Chain === | ||
{{Main|Mean Inequality Chain}} | {{Main|Mean Inequality Chain}} | ||
− | The '''Mean Inequality Chain | + | The '''Mean Inequality Chain''', also called the '''RMS-AM-GM-HM Inequality''', relates the root mean square, arithmetic mean, geometric mean, and harmonic mean of a list of nonnegative reals. In particular, it states that <cmath>\sqrt{\frac{x_1^2 + x_2^2 + \cdots + x_n^2}{n}} \geq \frac{x_1 + x_2 + \cdots + x_n}{n} \geq \sqrt[n]{x_1 x_2 \cdots x_n} \geq \frac{n}{\frac{1}{x_1} + \frac{1}{x_2} + \cdots + \frac{1}{x_n}},</cmath> with equality if and only if <math>x_1 = x_2 = \cdots = x_n</math>. As with AM-GM, there also exists a weighted version of the Mean Inequality Chain. |
=== Power Mean Inequality === | === Power Mean Inequality === | ||
{{Main|Power Mean Inequality}} | {{Main|Power Mean Inequality}} | ||
+ | The '''Power Mean Inequality''' relates every power mean of a list of nonnegative reals. The power mean <math>M(p)</math> is defined as follows: <cmath>M(p) = | ||
== Introductory examples == | == Introductory examples == |
Revision as of 20:23, 29 November 2021
In Algebra, the AM-GM Inequality, or more formally the Inequality of Arithmetic and Geometric Means, states that the arithmetic mean is greater than or equal to the geometric mean of any list of nonnegative reals; furthermore, equality holds if and only if every real in the list is the same.
In symbols, the inequality states that for any real numbers , with equality if and only if .
NOTE: This article is a work-in-progress and meant to replace the Arithmetic mean-geometric mean inequality article, which is of poor quality.
Contents
[hide]Proofs
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Generalizations
The AM-GM Inequality has been generalized into several other inequalities, which either add weights or relate more means in the inequality.
Weighted AM-GM Inequality
The Weighted AM-GM Inequality relates the weighted arithmetic and geometric means. It states that for any list of weights such that , with equality if and only if . When , the weighted form is reduced to the AM-GM Inequality. Several proofs of the Weighted AM-GM Inequality can be found in the proofs of AM-GM article.
Mean Inequality Chain
- Main article: Mean Inequality Chain
The Mean Inequality Chain, also called the RMS-AM-GM-HM Inequality, relates the root mean square, arithmetic mean, geometric mean, and harmonic mean of a list of nonnegative reals. In particular, it states that with equality if and only if . As with AM-GM, there also exists a weighted version of the Mean Inequality Chain.
Power Mean Inequality
- Main article: Power Mean Inequality
The Power Mean Inequality relates every power mean of a list of nonnegative reals. The power mean is defined as follows: The Power Mean inequality then states that if , then , with equality holding if and only if Plugging into this inequality reduces it to AM-GM, and gives the Mean Inequality Chain. As with AM-GM, there also exists a weighted version of the Power Mean Inequality.
Introductory examples
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Intermediate examples
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Olympiad examples
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More Problems
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