FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups 
 ProfileProfile   PreferencesPreferences   Log in to check your private messagesLog in to check your private messages   Log inLog in 
Forum index » Science and Technology » Math » num-analysis
Number Theory
Post new topic   Reply to topic Page 1 of 1 [2 Posts] View previous topic :: View next topic
Author Message
Peter L. Montgomery
science forum Guru Wannabe


Joined: 01 May 2005
Posts: 181

PostPosted: Sat Jul 15, 2006 7:24 pm    Post subject: Re: Number Theory Reply with quote

In article <30524459.1152932253418.JavaMail.jakarta@nitrogen.mathforum.org>
Danilo <danilorj@gmail.com> writes:
Quote:
Find all positive integers n so that 8n^3+36n^2+55n+23 is a perfect cube.
Thanks.

sci.math.num-analysis is for topics related to
numerical analysis, which typically involve
approximations and floating point arithmetic.
sci.math is more general. There is also a homework group
but I forget its name.

This said, look at your cubic f(n) = 8*n^3 + 36*n^2 + 55*n + 23
(it's much easier to read equations when you space
in accordance with operator precedence).
If m^3 = f(n), then m = f(n)^(1/3).
Since f(n) is about 8*n^3 for large n, m is about 2*n.
Find a better approximation for m when n is large.
Look for the needed conditions to make both m and n integers.
Do small values of n by a brute search, if needed.


--
Why do storms (e.g., Katrina) have human names,
while earthquakes (e.g., Loma Prieta) have place names?

pmontgom@cwi.nl Microsoft Research and CWI Home: Bellevue, WA
Back to top
Danilo
science forum beginner


Joined: 26 Mar 2006
Posts: 12

PostPosted: Sat Jul 15, 2006 2:57 am    Post subject: Number Theory Reply with quote

Find all positive integers n so that 8n^3+36n^2+55n+23 is a perfect cube.
Thanks.
Back to top
Google

Back to top
Display posts from previous:   
Post new topic   Reply to topic Page 1 of 1 [2 Posts] View previous topic :: View next topic
The time now is Mon Oct 23, 2017 11:19 am | All times are GMT
Forum index » Science and Technology » Math » num-analysis
Jump to:  

Similar Topics
Topic Author Forum Replies Last Post
No new posts how to deduce a number validation algorithm? Tim_Mac Math 1 Fri Jul 21, 2006 10:43 am
No new posts a subset of natural number levine121323@yahoo.com Math 1 Fri Jul 21, 2006 6:17 am
No new posts unified theory gb6724 New Theories 4 Fri Jul 21, 2006 5:25 am
No new posts Signal Nonlocality Loophole in Quantum Theory? Jack Sarfatti Math 0 Thu Jul 20, 2006 1:59 am
No new posts A Combinatorics/Graph Theory Question mathlover Undergraduate 1 Wed Jul 19, 2006 11:30 pm

Copyright © 2004-2005 DeniX Solutions SRL
Other DeniX Solutions sites: Electronics forum |  Medicine forum |  Unix/Linux blog |  Unix/Linux documentation |  Unix/Linux forums  |  send newsletters
 


Powered by phpBB © 2001, 2005 phpBB Group
[ Time: 0.0180s ][ Queries: 20 (0.0048s) ][ GZIP on - Debug on ]