Difference between revisions of "Maclaurin's Inequality"

Revision as of 14:19, 26 October 2007

Maclaurin's Inequality is an inequality in symmetric polynomials. For notation and background, we refer to Newton's Inequality.

For non-negative $x_1, \ldots, x_n$ ,

$d_1 \ge d_2^{1/2} \ge \ldots \ge d_n^{1/n}$ ,

with equality exactly when all the $x_i$ are equal.

By the lemma from Newton's Inequality, it suffices to show that for any $n$ ,

$d_{n-1}^{1/(n-1)} \ge d_{n}^{1/n}$ .

Since this is a homogenous inequality, we may normalize so that $d_n = \prod x_i = 1$ . We then transform the inequality to

$\frac{\sum 1/x_i}{n} \ge 1^{\frac{n-1}{n}} = 1$ .

Since the geometric mean of $1/x_1, \ldots, 1/x_n$ is 1, the inequality is true by AM-GM.

@@ Line 33: / Line 33: @@
 * [[Symmetric sum]]
-[[Category:Number Theory]]
+[[Category:Inequality]]
 [[Category:Theorems]]
-[[Category:Definition]]