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Article #60Re: Help on a Maths problem
From: John Porcella
Date: Sun, 30 Jun 2002 21:47
Date: Sun, 30 Jun 2002 21:47
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2618 bytes
"Mot" <thomas.sirvent+news@ANTISPAMpolytechnique.org> wrote in message news:afnacq$10f8$1@f1node01.rhrz.uni-bonn.de... > Thank you for sharing this messagee on lots of newsgroups... > Theoretically, you don't have to speak english on french newsgroups : there > is no reason to post there... > > The answer to your question : > > you can take B very Big and : > B * (12/B) = 12 > B + (12/B) > B which can be taken as big as you want... > So, there is no maximum value... > > You intend to minimize a + b when a * b = 12 > You have so to study f : x -> x + 12/x > and find its minimum value for x > 0... > > f ' (x) = 1 - 12/x� > f ' (x) = 0 if x = sqrt(12) and this is a minimum... To ascertain whether it is a minimum, a maximum or simply a point of inflection, you need to take the second derivative (or so I have just been taught): f" (x): 12/x^3...and since THIS is positive, then 2 sqrt (3) is a minimum. -- MESSAGE ENDS. John Porcella
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X-Google-Language: ENGLISH,ASCII X-Google-Thread: f458d,44c41f9a378f83c0 X-Google-Attributes: gidf458d,public X-Google-Thread: 1139f8,44c41f9a378f83c0 X-Google-Attributes: gid1139f8,public X-Google-Thread: 10a31a,44c41f9a378f83c0 X-Google-Attributes: gid10a31a,public X-Google-Thread: 106622,44c41f9a378f83c0 X-Google-Attributes: gid106622,public X-Google-Thread: f45a7,44c41f9a378f83c0 X-Google-Attributes: gidf45a7,public X-Google-Thread: 112e06,44c41f9a378f83c0 X-Google-Attributes: gid112e06,public X-Google-ArrivalTime: 2002-06-30 14:48:09 PST Path: arc1-ca.pugleaf.net!archiver1.google.com!news1.google.com!sn-xit-02!sn-xit-06!supernews.com!news.maxwell.syr.edu!news.mailgate.org!btnet-peer0!btnet-feed5!btnet!news.btopenworld.com!not-for-mail From: "John Porcella" <bronson69@btinternet.com> Newsgroups: alt.school.homework-help,fr.education.entraide.maths,fr.sci.maths,uk.education.maths,uw.math.mathsoc,york.mathstat.course.math2221 Subject: Re: Help on a Maths problem Date: Sun, 30 Jun 2002 21:47:40 +0000 (UTC) Organization: BT Openworld Lines: 34 Message-ID: <afnu9s$aqk$1@paris.btinternet.com> References: <3d1eedb4$0$25797$afc38c87@news.optusnet.com.au> <afnacq$10f8$1@f1node01.rhrz.uni-bonn.de> NNTP-Posting-Host: host213-122-203-47.in-addr.btopenworld.com X-Trace: paris.btinternet.com 1025473660 11092 213.122.203.47 (30 Jun 2002 21:47:40 GMT) X-Complaints-To: news-complaints@lists.btinternet.com NNTP-Posting-Date: Sun, 30 Jun 2002 21:47:40 +0000 (UTC) X-Newsreader: Microsoft Outlook Express 6.00.2600.0000 X-MSMail-Priority: Normal X-Priority: 3 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2600.0000