Talk:Completing the square

message: It looks like completing the square can be used to find the inverse:
f(x) = a(x-h)^2 + k
rearranging:
f-1(x) = h+-sqrt((f(x)-k)/a)    :i.e. the inverse.  For some reason finding a standard form for the inverse on the internet is rather harder than finding roots. 
Can we add this to this page?
159.245.32.2 (talk) 18:49, 16 May 2011 (UTC)
thread_title:  Inverse Quadratic  

message: Please verify the complete the square formula. I changed the page (before I had an account) by altering the equation to what I believe is the correct form, on 9/25/2006. Specifically, I changed the part of the equation that read: "4a^2" to "4a". I made this change while doing some calc II homework, when I realized that I was getting incorrect results with the equation that was on the page prior to my change on 9/25/2006.
After looking a bit further, I realized that the equation had previously been entered correctly, but some user (Huadpe) "corrected" the equation later to the "wrong" value: 4a^2. Although I think the equation is correct now, I'd appreciate it if a more veteran user/moderator of wikipedia with solid math knowledge could confirm the accuracy of the equation on the page, and somewhere make a public note (or cite) to that effect.
I'm a very experienced user of google and also a computer science major, yet I had difficulty finding a simple "plug-and-play" equation that would algebraically provide a completed square given the coefficients a, b, and c from ax^2 + bx + c. After much searching, I found that Wikipedia provided this equation, but it happened to have this minor error. I fear that other math students (likely at lower levels of math, or perhaps some that need refreshers like me) are likely to come to this page as their primary source in the future, and the equation will be modified to the incorrect version again. I'm not sure how wikipedia prevents this, but please put this on your "watch list".
Thanks all!
Austin
Austinflorida 09:23, 21 October 2006 (UTC)
thread_title:  Please verify the complete the square formula 

message: Does completing the square also apply to multivariate equations?  The procedure is the same, say you have: x^{2} - 4xy + 5y^{2} = (x-2y)^{2} + y^{2},
This corresponds to completing the square with x, holding y constant - nothing too extraordinary.
However, you can extend this process to three variables.  Take for example 
 x^{2} + 4xy + 8y^{2} + 20yz + 6z^{2} -4xz = (x + 2y - 2z)^{2} + (2(y+3z))^{2} - 34z^{2} , (if my algebra is correct!)  This is also an application of completing the square, allowing us to write a quadratic polyomial of three variables in which all terms have degree two, as the sum of three squares.
(My inspiration was a multivariate calculus problem: 
Create a tranformation to map the ellipsoid x^{2} + 4xy + 8y^{2} +4yz + 6z^{2} - 2xz = 9, onto the unit sphere.)
--D Mac 04:39, 17 November 2005 (UTC)
thread_title:  Questions / Possible Additions to the Article 

message: Last evening, an anon user blanked this page. I reverted it and warned the user. Please pay special attention to this page on your watch list to spot any future vandalism. 48v 00:10, 5 September 2006 (UTC)
thread_title: Vandalism

message: I just did a significant reorganization of this article.  I changed very little content, but added an Overview section heading for everything that was in the intro previously but for its first paragraph, moved the canonical quadratic equation to its own example, and subsectioned out and reordered the several examples (from most specific to most general).  I tweaked a lot of math markup to look nicer, and changed the discourse on just manipulating a x^2 + b x + c to actually finding its roots, as this is arguably the most significant application of the topic (which I also noted).
I was considering removing some examples for space, perhaps what are now the second and fourth.  But I decided to let this version stand and see what comments came first.  Baccyak4H 16:38, 27 October 2006 (UTC)
thread_title:  Reorganization 

message: I've done a major cleanup, taking advantage of the new and improved texvc, which can now handle the "align" environment. Along the way I polished the prose and pruned the examples. I did not touch the intro, though it needs work. --KSmrqT 08:52, 26 November 2006 (UTC)
thread_title:  Cleanup 

message: Where is that equation to complete squares?  — Preceding unsigned comment added by Pasanbhathiya2 (talk • contribs) 17:30, 10 December 2010 (UTC)
replies: text: I have removed the equation. This is about the polynomial ax2+bx+c. It is not about the equation ax2+bx+c=0. So the values of x which you added are not really relevant in this context. See my edit summary and a note on your talk page. DVdm (talk) 20:26, 10 December 2010 (UTC)
thread_title: Where is that equation?

message: The bit that begins 'The matrix case looks very similar:' tempts the question what matrix case?  Matrices have not been previously mentioned.  That, and other things, makes the article look as if many different people have just thrown in odd bits here and there.  Note that someone who really needs to know how to complete the square is probably rather new to mathematics, and clarity is essential for such a person.  — Preceding unsigned comment added by 81.131.57.37 (talk) 15:29, 21 October 2012 (UTC)
thread_title:  The matrix case 

message: See the discussion here. Jarble (talk) 02:56, 6 January 2015 (UTC)
thread_title: This article appears to contradict another article

message: Can we please not use the variable "a" for the area.  This will confuse any students stupid enough to expect to learn anything from Wikipedia maths article because "a" is normally the coefficient of the x^2 term.  "k", or "-c" would be fine.  I know that this will not confuse expert mathematicians, but experts already know this stuff. Tuntable (talk) 00:27, 8 February 2021 (UTC)
replies: text: I second this, but the graphic would have to be updated accordingly, so I cannot make the change myself as I am not familiar with how to deal with images on wikipedia Joel Brennan (talk) 11:27, 13 May 2021 (UTC)
thread_title:  Completing the Square geometry 

message: — Assignment last updated by Ahlluhn (talk) 00:57, 31 May 2024 (UTC)
thread_title: Wiki Education assignment: 4A Wikipedia Assignment