Talk:Nth root

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Mathematics rating:
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Field:  Algebra

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Section 7.1 states "which can be modified in various ways as described in that article". What article? — Preceding unsigned comment added by 2.244.149.31 (talk) 17:57, 25 August 2016 (UTC)

"Quantities left uncomputed under a radical sign are also called surds." This is not correct. Surds are strictly irrationals.

This article talks about "surds" before defining what they are. - dcljr 06:03, 6 Aug 2004 (UTC)

This article also perports to define the term radical, and at no point does it directly do so. - Preceding unsigned comment posted by 201.130.133.221, April 10, 2006.Cliff (talk) 06:28, 22 March 2011 (UTC)

The section, 'Finding all the roots', tells us how to find all the roots in terms of the principle root and n, but the only definition for the princinple root used in the article is the one which is always a real number and doesn't always exist. Someone needs to put in a bit about the extension to complex numbers. There is actual more on the cube root page. - Preceding unsigned comment posted by 82.46.105.162, May 26, 2006.Cliff (talk) 06:28, 22 March 2011 (UTC)

Done! —Mets501talk 01:04, 27 May 2006 (UTC)

Cool, thanks. - Preceding unsigned comment posted by 82.46.105.162, May 27, 2006.Cliff (talk) 06:28, 22 March 2011 (UTC)

Initial author in this section was ignored. Does anybody have verification of his interpretation of the term Surd? If he is correct, the article still incorrectly covers the term. Cliff (talk) 06:30, 22 March 2011 (UTC)

Merge

I think this article and N-th root are the same thing, just under different names!

++++++++++++++++gavan

shouldn't the equation for finding the nth root be on this page?? 'twould be useful to say the least (not to mention relevant) ${\displaystyle x^{(}1/n)=e^{(}(lnx)/n)}$

Edit: Simon Fendall This relates to the merge somewhat. When visiting the N-th Root this does not exist, but when visiting the Nth Root under surds it shows ${\displaystyle ({a}/{sqrt(b)})({sqrt(b)}/{sqrt(b)})=a*sqrt(b)}$ Which appears to be wrong. —Preceding unsigned comment added by 125.238.148.208 (talk) 22:24, 3 March 2008 (UTC)

Pronunciation?

I believe this page would be beneficial if it also contained correct pronunciation examples of nth roots.

For example, how do you say 4√200 ? I believe the only correct way to say it is 200 to the fourth root, however maybe some could clarify this.

It is "the fourth root of 200". --Professor Fiendish (talk) 02:21, 21 August 2009 (UTC)

I added some information related to finding products and quotients of radicals w/ different indices and how to simplify indices. I believe the examples I used are correct, if not my apologies and permission (request) to change it ASAP. Nevertheless, I am not quite sure I have written in the correct section. Should it be moved to the section dealing with surds, or should it remain in the 'basic operations' section? -- Ishikawa Minoru 22:06, 7 June 2007 (UTC)

Finding all roots

The formulas for finding the roots in the article are confusing. What is given in the article is not really an equation, as it has no result (i.e., it is merely an expression). Further, having ${\displaystyle {\sqrt[{n}]{a}}}$ appear in the formula is confusing, as that is the result one is trying to find. Should the formula rather be written as the following (guessing), like it is in Nth root algorithm?

${\displaystyle x_{k+1}=e^{({\frac {\phi +2\pi k}{n}})i}\times x_{k}}$

Also, φ and the "Euler's equation form" should really be defined/expressed in the article. Readers shouldn't have to do this level of research in order to understand an encyclopedia article. SharkD (talk) 08:10, 20 February 2008 (UTC)

This section is about as clear as mud, but if there were any mathematicians reading this, they'd simply criticize your education for your ignorance of Euler's formula and how it should be interpreted when it appears in aeiφ In Euler's formula, φ is defined as being equal to "atan2(y,x)", where y is the imaginary part of a complex number z, and x is the real part of z. It is far from clear whether z should be replaced with a in this incarnation of the formula, or whether z is some variable that has nothing whatsoever to do with a. It is also not clear whether the formula aeiφ really works for real numbers, since Euler's formula is clearly meant to be used for complex numbers.
As for ${\displaystyle {\sqrt[{n}]{a}}}$ appearing in the definition, the algorithm requires the principal nth root of a as an input (use Nth root algorithm to find that root). The algorithm being defined merely finds the other nth roots.

98.31.14.215 (talk) 14:16, 15 August 2008 (UTC)

Fifth root extraction

I deleted this section because it did not seem appropriate to an encyclopedia article Gary (talk) 17:13, 29 May 2008 (UTC)

Only for reals

This identity does not work for non-real complex numbers:

• ${\displaystyle {\frac {\sqrt {a}}{\sqrt {b}}}={\sqrt {\frac {a}{b}}}}$

76.90.9.68 (talk) 05:53, 3 July 2008 (UTC)

Well, you changed "positive number" to "positive real number", but I am not sure I see the point of that additional qualification. Can you give an example of a positive number that is not real ? Gandalf61 (talk) 09:20, 22 March 2011 (UTC)
in some sense of the word, 2i+2 is a "positive" complex number, residing in the first quadrant of the complex plane. Three of the four quadrants can be considered to be positive depending on context. Positive is quite ambiguous and does not imply a real number. Cliff (talk) 15:27, 22 March 2011 (UTC)
Not in any useful or standard sense of the word, because (2i+2)5 = -128 - 128i, and you have the unfortunate spectacle of a power of a "positive" number becoming "negative". There is no way to categorise general complex numbers as positive and negative that always respects the laws positive x positive = positive etc. To a mathematician, "positive number" always implies that the number is real. Gandalf61 (talk) 15:53, 22 March 2011 (UTC)
Not all readers of this page are mathematicians. In fact, I'll guess that of the people who search for this page and find it, most are not mathematicians. To the general reader, positive only means "not having a negative sign". For instance, if you asked the general reader whether -y is positive or negative, the answer would almost universally be "negative", ignoring the actual value of y. Thus, the minor addition to the section in question. Cliff (talk) 17:08, 22 March 2011 (UTC)
I guess "real" doesn't hurt, although I had never heard of anyone referring to 2+2i as "positive" before. — Arthur Rubin (talk) 21:35, 22 March 2011 (UTC)

Are "almost all" square roots of rationals irrational?

Off the top of my head, it seems that square roots of irrationals must be irrational themselves, because if the root were rational the numerator and denominator could be squared to give a rational number (and we've already said the original must be irrational). However, what about the rationals? Assume a rational number x = a/b, in lowest terms. Here's what I come up with:

1) Sqrt(x) will be rational if and only if sqrt(a) and sqrt(b) are rational. 2) Square roots of integers such as a and b are rational if and only if the number is a perfect square. 3) Perfect squares are in a one-to-one correspondence with the natural numbers, as every natural number has a perfect square and there are no perfect squares which are not the square of a natural number. 4) We can safely limit the discussion to whole numbers, as the case x = 0/b is trivial and x = a/0 isn't within the domain of algebra, and all negative numbers would have the same square as their positive counterpart.

Ultimately, then, the question is: Given two coprime whole numbers a and b, what are the odds that both of them are perfect squares? Have I missed anything, and is the answer to the above question known? 72.236.7.161 (talk) 23:45, 11 April 2009 (UTC)

Of course, the answer is known. This is really a trivial problem. Suppose x=a/b where a and b are integers and b>0. Then x=a·b/(b2). So x is the square of a rational number if and only if a·b is the square of an integer. JRSpriggs (talk) 05:40, 12 April 2009 (UTC)

Solving Polynomials

In the Solving Polynomial section, the link to elementary operations currently redirects to elementary matrix. I am not an expert in the subject, so such a redirection may be completely expected to one versed in mathematics, however, my expectation of the link based on its title alone would yield the "elementary operations" of Arithmetic. I suspect that the link may have been added before a move or without verification of the linked content. If the current link is most appropriate, I might suggest changing the linked text to "elementary matrix operations" or something similar.

99.190.84.136 (talk) 23:19, 28 June 2009 (UTC)

You're right, it does indeed refer to the elementary operations of arithmetics. Thanks for bringing this to our attention; I now changed it to point to elementary arithmetic. Cheers, Jitse Niesen (talk) 16:11, 29 June 2009 (UTC)

Arabic

The article says:

the first letter in the word (Jathir, [with the "th" pronounced like the "th" in the english word "the"] in Arabic means root)

I think that it is not exact.

In my dictionary (Al-Mawrid 2004), the word is جَذْر, which is pronounced jaḏr. --Amir E. Aharoni (talk) 11:28, 3 September 2009 (UTC)