Talk:Quadratic form

From Wikipedia, the free encyclopedia

Perhaps it would also be helpful to add the case of one variable? I say this because most of the general public will deal only with this case in high school and the first year of college calculus. Like so:

F(x) = ax² + bx + c

However I don't feel quite comfortable enough mathematically to actually modify the article, so if someone smart would like to implement this, I'd enjoy that :)

Goodralph 10:15, 3 Mar 2004 (UTC)

That's not a quadratic form, but a quadratic function q.v.

Charles Matthews 11:07, 3 Mar 2004 (UTC)

Added comment to that effect to article. - dcljr 06:51, 24 Feb 2005 (UTC)

Indeed quadradic forms must be homogeneous of degree 2 i.e. the sum of the exponents in each term must be 2.

Indeed quadradic forms must be homogeneous of degree 2 i.e. the sum of the exponents in each term must be 2.

[edit] Quadratic forms in Statistics

We need a either a section or an article on the properties of quadratic forms used in statistics. There are about a half dozen important theorems about these. For example, if g is a vector of constants, ε is a random vector whose entries are independent with variance σ², and y = g + ε, then . I think there is enough to warrant a separate article on this; are there any objections? Btyner 18:41, 27 November 2005 (UTC)

[edit] error in isotropic defn?

The definition of isotropic and anisotropic in this article appears to be reversed, at least to me. It defines an "isotropic space" as one whose form has a non-trivial kernel. Surely such a space should be anisotropic, instead? That defn has been there a longgg time. linas 13:11, 19 July 2006 (UTC)

The definition in the article seems to agree with J. P. Serre in "A Course in Arithmetic" (interesting title!), so Isuspect it might be right. Madmath789 14:57, 19 July 2006 (UTC)

The definition is correct. Isotropic is the standard name for spaces with non zero elements v such that Q(v) = 0. This is according to the refrence listed on the bottom of the article.

[edit] Start out simple

This article is a confusing read. It should start out presenting some simple results about symmetric matrices. 80% percent of the readers will be looking for these results, so they should be presented first.

Very few readers will be interested in topology and number theory. Therefore these sections should be moved to a section near the end or possibly transferred to a separate article.