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The contents of the Substitution of variables page were merged into Change of variables on 2013-1-23. For the contribution history and old versions of the redirected page, please see its history; for the discussion at that location, see its talk page. |
There is an error at the "Simple example" section. It is written that x+y=55 xy=16 don't give a solution while they actually do. And the solution is (x;y)=(0.29246;54,70754). I've written it with some degree of accuracy, but I guess it is not OK to be written this way, but I think it's better than the statement that these equations have no solution at all! — Preceding unsigned comment added by EMoMaD ( talk • contribs) 22:18, 16 September 2013 (UTC)
Can someone clarify the steps in the example in the Differentiation section? Cause I think I'm missing something during the breakdown of d/dx, specifically what happened to d/dx of x^2 and how that transformed into 2x. -- ( Mrja84 ( talk) 18:52, 2 August 2009 (UTC))
Why would someone make such a strange formula as an intro? —Preceding unsigned comment added by 128.250.5.246 ( talk) 08:45, 9 March 2010 (UTC)
In what sense is that an 8th order polynomial? The highest degree of any term is 6!
-- watson ( talk) 22:15, 27 March 2010 (UTC)
It seems to me that the topic of the article Substitution of variables (a term I don't remember encountering before) is the same as the topic treated here. -- Lambiam 19:11, 14 September 2011 (UTC)
A 6th order polynomial has six roots. How can we find the complete roots by the proposed substitution? Only the roots x=1 and x=2 are calculated.-- Kaktus Kid ( talk) 20:24, 23 May 2012 (UTC)
The article substitution (algebra) has been merged incorrectly to this one: The term "substitution" was not defined after the merge, and the tag "merge proposal" has not been removed. I have not reverted the merge, but I have included in the lead a definition of "substitution" and clarified its relation with change of variable. I have not a clear opinion on the best solution (one or two articles). D.Lazard ( talk) 16:39, 7 January 2014 (UTC)
I also think the intro needs a lot of work and clarification. It is really hard to get anything out of it. In particular, the first paragraph is hard to understand. Compare with Alpha:
In other words, an expression involving free variables may be considered as defining a function, and substituting values to the variables in the expression is equivalent to applying the function defined by the expression to these values.
v
A theorem which effectively describes how lengths, areas, volumes, and generalized n-dimensional volumes (contents) are distorted by differentiable functions.
The second is succinct, and gives an impression of how it is used, and doesn't take 10 minutes to parse. That being said, I am not an expert on calculus, so I need to appeal to others for clarification. — Preceding unsigned comment added by OceanEngineerRI ( talk • contribs) 19:56, 8 July 2016 (UTC)
The article plug and chug redirects here, but that is clearly wrong -- plug and chug is about the algorithmic solution to a problem, by carrying out proof steps -- its low-brow version of what would be called proof theory in high-brow terms. In low-brow terms, its what engineering students do, when they find some equation in a textbook, and then plug in numbers, pull out their (ahem) modern-day slide-rule and see where they end up. This clearly is not a change of variables! 67.198.37.16 ( talk) 18:36, 26 September 2016 (UTC)