1611688965-49eb25192487de9ca8a71123a3c272a8 (826653), страница 12
Текст из файла (страница 12)
®£¤ , ¯®«®¦¨¢ ¢ ä®à¬ã«¥ (4.3)(x) = f 0 1(x) , ¬ë ¯®«ã稬 ãà ¢¥¨¥ ¢¨¤ (4.2): ª ª ªx = x ff(x)0 (x) (x):0 2 f(x)f 00 (x) f(x)f 00 (x)0 (x) = 1 (f (x))(f 0 (x))= (f 0 (x))2 ;2â® 0 (x) = 0. ¥âà㤮 ã¡¥¤¨âìáï, çâ®, ¢®®¡é¥ £®¢®àï,00(x ) 6= 0, â. ¥. ᮣ« ᮠ⥮६¥ 4.5 ¨â¥à æ¨®ë© ¬¥â®¤n)xn+1 = xn ff(xn = 0; 1; : : :;(4:15)0 (xn ) ; §ë¢ ¥¬ë© ¬¥â®¤®¬ ìîâ® , ¨¬¥¥â ¢â®à®© ¯®à冷ª á室¨¬®áâ¨. ¬¥â¨¬, çâ® § 票¥ xn+1 ¥áâì ¡áæ¨áá â®çª¨ ¯¥à¥á¥ç¥¨ï á ®áìî Ox ª á ⥫쮩, ¯à®¢¥¤¥®© ¢ â®çª¥ (xn; f(xn ))ª £à 䨪ã äãªæ¨¨ f(x) (á¬.
à¨á. 4.4). ¬¥® ¯®í⮬㠬¥â®¤ìîâ® §ë¢ îâ â ª¦¥ ¬¥â®¤®¬ ª á ⥫ìëå.¨á. 4.4. ¥â®¤ ìîâ® «ï ®æ¥ª¨ ᪮à®á⨠á室¨¬®á⨠¬¥â®¤ ìîâ® à §«®¦¨¬ äãªæ¨î f(x) ¢ àï¤ ¥©«®à ¢ ®ªà¥áâ®á⨠â®çª¨ xn :840 = f(x ) = f(xn ) + f 0 (xn)(x xn ) + 21 f 00 ()(x xn )2;£¤¥ «¥¦¨â ¬¥¦¤ã xn ¨ x . ç¨â,f(xn ) = x x 1 f 00 () (x x )2:f 0 (xn ) n 2 f 0 (xn ) n®¤áâ ¢«ïï íâ® ¢ëà ¦¥¨¥ ¢ ä®à¬ã«ã (4.15), ¯®«ã稬n ) = 1 f 00 () (x x )2 :xn+1 x = xn x ff(x0 (xn) 2 f 0 (xn) nâáî¤ M2 jx x j2 ;jxn+1 xj 2mn1£¤¥ m1 = x2minjf 0 (x)j, M2 = xmaxjf 00 (x)j.[a; b]2[a; b]®¥ç®, ¯®«ãç¥ ï ®æ¥ª ¬®¦¥â £ à â¨à®¢ âì ª¢ ¤à â¨çãî á室¨¬®áâì ¬¥â®¤ «¨èì ç¨ ï á ⮣® ®¬¥à M2 jx x j < 1. n, ¤«ï ª®â®à®£® ¢ë¯®«ï¥âáï ãá«®¢¨¥ 2mn1ç «ì®¥ ¯à¨¡«¨¦¥¨¥ x0 ¦¥« â¥«ì® ¢ë¡¨à âì â ª, ç⮡먬¥«® ¬¥áâ® ¥à ¢¥á⢮f(x0 )f 00 (x0 ) > 0;¨¡® ¢ ¯à®â¨¢®¬ á«ãç ¥, ª ª ¢¨¤® ¨§ à¨á.
4.5, ᫨誮¬¡®«ìè ï ç «ì ï ¯®£à¥è®áâì jx0 x j ¬®¦¥â ¯à¨¢¥á⨪ ⮬ã, çâ® ¨â¥à æ¨®ë© ¯à®æ¥áá ¥ ¡ã¤¥â á室ï騬áï.¨á. 4.5. á室¨¬®áâì ¬¥â®¤ ìîâ® 85®áâ â®çë© ¯à¨§ ª á室¨¬®á⨠¬¥â®¤ ìîâ® áä®à¬ã«¨à®¢ ¢ á«¥¤ãî饩 ⥮६¥ (¯à¥¤¯®« £ ¥âáï, çâ® x |¥¤¨áâ¢¥ë© ª®à¥ì ãà ¢¥¨ï (4.1) ®â१ª¥ [a; b]).¥®à¥¬ 4.6. ãáâì ¤«ï ¢á¥å x 2 [a; b] ¢ë¯®«¥® ¥à -¢¥á⢮f 0 (x)f 00 (x) > 0:®£¤ ¨â¥à 樮 ï ¯®á«¥¤®¢ ⥫ì®áâì, ¯®áâ஥ ﯮ ¬¥â®¤ã ìîâ® ¯à¨ 0, ¬®®â®® ã¡ë¢ ¥â ¨á室¨âáï ª . ᫨ ¦¥ ¤«ï ¢á¥å¢ë¯®«¥® ¥à ¢¥á⢮xx = bx 2 [a; b]f 0 (x)f 00 (x) < 0;â® ¨â¥à 樮 ï ¯®á«¥¤®¢ ⥫ì®áâì, ¯®áâ஥ ï ¯® ¬¥â®¤ã ìîâ® ¯à¨ 0, ¬®®â®® ¢®§à á⠥⠨ á室¨âáï ª .x ¤ ç 4.3.x =a®ª § âì ⥮६ã 4.6.ª § ¨¥.
®á¯®«ì§®¢ âìáï ä®à¬ã«®© ª®¥çëå ¯à¨à 饨© £à ¦ .¤¨ ¨§ á«ãç ¥¢ ¬®®â®®© á室¨¬®á⨠¬¥â®¤ ìîâ® ¡ë« ¯à®¤¥¬®áâà¨à®¢ à¨á. 4.4.¯¨è¥¬ ¯à®á⮩ ¯à¨¥¬ ª®â஫ï â®ç®á⨠¢ ¬¥â®¤¥ ìîâ® . ª ª ª, ᮣ« á® ä®à¬ã«¥ ¥©«®à ,f(xn ) = f(xn ) f(x ) = (xn x )f 0 (), â®n )jjxn x j jf(x(4:16)m1 :⠮楪 ¯®§¢®«ï¥â ª ¦¤®¬ è £¥ á«¥¤¨âì § ¤®á⨣ã⮩ â®ç®áâìî. ª®¥æ § ¬¥â¨¬, çâ® ¢¡«¨§¨ ªà ⮣® ª®àï ¬®¦¥â ¡«î¤ âìáï òà §¡®«âª ó ç¨á«¥®£® à¥è¥¨ï ¢¢¨¤ã ¯®â¥à¨â®ç®á⨠¨§-§ ®è¨¡®ª ®ªà㣫¥¨ï ¯à¨ ¢ëç¨á«¥¨¨ ®â®è¥¨ï ¤¢ãå ¬ «ëå ¢¥«¨ç¨.
®í⮬ã á«¥¤ã¥â ¯à¨¬¥ïâì ¯à¨¥¬ ࢨª . â® ®â®á¨âáï ¨ ª ¤à㣨¬ ¬¥â®¤ ¬ ¢ë᮪®£® ¯®à浪 .864.3.2. ¯¨è¥¬ àï¤ ¨â¥à 樮ëå ¬¥â®¤®¢, ¯®«ãç îé¨åáï ¯ã⥬ ã¯à®é¥¨ï ¬¥â®¤ ìîâ® . í⮬ ¯ãªâ¥ ¬ë ¡ã¤¥¬¯®« £ âì, çâ® äãªæ¨ï f ¨ ¥¥ ¯à®¨§¢®¤ë¥ ®¡« ¤ î⠢ᥬ¨ ᢮©á⢠¬¨, ª®â®àë¥ ¥®¡å®¤¨¬ë ¤«ï ¯à¨¬¥¥¨ï ¬¥â®¤ ìîâ® (á¬. ç «® ¯ãªâ 4.3.2).â®¡ë ¨§¡¥¦ âì ¢ ä®à¬ã«¥ (4.15) ¬®£®ªà ⮣® ¢ëç¨á«¥¨ï ¯à®¨§¢®¤®© f 0 (x), ¨á¯®«ì§ãîâ ¬®¤¨ä¨æ¨à®¢ ë© ¬¥â®¤ ìîâ® :n)xn+1 = xn ff(xn = 0; 1; 2; : : :0 (x0) ;祢¨¤®, íâ®â ¬¥â®¤ ï¥âáï ç áâë¬ á«ãç ¥¬( = 1=f 0 (x0 )) ¬¥â®¤ ५ ªá 樨, ãá«®¢¨ï á室¨¬®á⨠ª®â®à®£® ¯à¨¢¥¤¥ë ¢ ¯. 4.3.1.
«ï ¨å ¢ë¯®«¥¨ï ¥®¡å®¤¨¬®,¢ ç áâ®áâ¨, ç⮡ë ç «ì®¥ ¯à¨¡«¨¦¥¨¥ x0 㤮¢«¥â¢®àï«®âॡ®¢ ¨îjf 0 (x0)j > M21 :®á«¥¤¥¥ ¥à ¢¥á⢮ áà §ã á«¥¤ã¥â ¨§ ãá«®¢¨ï (4.13) ( ¯®¬¨¬, çâ® M1 = max jf 0 (x)j). ª¨¬ ®¡à §®¬, ¬®¤¨ä¨æ¨à®¢ ë© ¬¥â®¤ ìîâ® ¯à¥¤êï¥â ¬¥ìè¥ âॡ®¢ ¨© ª ¢ë¡®àã ç «ì®£® ¯à¨¡«¨¦¥¨ï x0, ® ¨¬¥¥â «¨èì ¯¥à¢ë© ¯®à冷ª á室¨¬®áâ¨. ª ¢¨¤® ¨§ à¨á.
4.6, ¯¥à¢®¬ è £¥ ¬®¤¨ä¨æ¨à®¢ ®£® ¬¥â®¤ ìîâ® áâநâáï ª á ⥫ì ï ª £à 䨪ã äãªæ¨¨f(x) ¢ â®çª¥ x0, ¯®á«¥¤ãîé¨å è £ å | ᥪã騥, ¯ à ««¥«ìë¥ í⮩ ª á ⥫쮩.¨á. 4.6. ®¤¨ä¨æ¨à®¢ ë© ¬¥â®¤ ìîâ® 87 ᫨ ¢ ¬¥â®¤¥ ìîâ® (4.15) ¯¯à®ªá¨¬¨à®¢ âì f 0 (xn)0)ª®¥ç®-à §®áâë¬ ®â®è¥¨¥¬ f(xxn ) f(x, â® ¯®«ã稬xn0¬¥â®¤ å®à¤:0xn+1 = xn f(xxn) xf(xf(xn ); n = 1; 2; : : :n0) ¥ª®â®àëå ª¨£ å íâ®â ¬¥â®¤ §ë¢ îâ ò¬¥â®¤®¬ ᥪãé¨åó, ®, ª ª ¬ë 㢨¤¨¬ çãâì ¨¦¥, ¯®á«¥¤¥¥ §¢ ¨¥ «®£¨ç¥¥ ¨á¯®«ì§®¢ âì ¤«ï ¤à㣮£® ¬¥â®¤ . ª ç¥á⢥ x0 ¢ë¡¨à îâ â®çªã, ¢ ª®â®à®© f(x0 )f 00 (x0)> 0. ç «ìë¬ ¯à¨¡«¨¦¥¨¥¬ ä ªâ¨ç¥áª¨ ï¥âáï ¥ª®â®à ïâ®çª x1, 㤮¢«¥â¢®àïîé ï ãá«®¢¨î f(x1 )f(x0 ) < 0.
®á«¥¤ãî騥 ¨â¥à 樨 ®áãé¥á⢫ïîâáï ®¡ëçë¬ á¯®á®¡®¬.â®¡ë ®¯à¥¤¥«¨âì ãá«®¢¨ï á室¨¬®á⨠¬¥â®¤ å®à¤, § ¬¥â¨¬, çâ® ¢ ¤ ®¬ á«ãç ¥x0 f(x) = x0f(x) xf(x0 ) ;(x) = x f(x)x f(xf(x) f(x0 )0)â® ¥áâì0 (x ) =0 ) f(x0 )) f 0 (x )(x0 f(x ) x f(x0 )) == (x0f (x ) f(x0 ))(f(x(f(x ) f(x0 ))2 x0)f 0 (x ) := f(x0 ) + (xf(x0) ¤à㣮© áâ®à®ë, ¯® ä®à¬ã«¥ ¥©«®à 2f(x0 ) + (x x0 )f 0 (x ) = (x0 2!x ) f 00 ():¥¬ á ¬ë¬2 00f () :0(x ) = (x0 2 x ) f(x)0롨à ï x0 ¤®áâ â®ç® ¡«¨§ª¨¬ ª x, ¬ë ¬®¦¥¬ ¤®¡¨âìáï¢ë¯®«¥¨ï ¥à ¢¥á⢠0 (x) q < 1 ¢ ¥ª®â®à®© ®ªà¥áâ®á⨠â®çª¨ x , çâ® ®¡¥á¯¥ç¨â á室¨¬®áâì ¬¥â®¤ å®à¤ á ¯¥à¢ë¬ ¯®à浪®¬, ¯à¨ í⮬ ¤«ï ®æ¥ª¨ â®ç®á⨠¬®¦¥â ¡ëâì¨á¯®«ì§®¢ ® ¥à ¢¥á⢮ (4.16).88¨á.
4.7. ¥â®¤ å®à¤¥®¬¥âà¨ç¥áª ï âà ªâ®¢ª ¬¥â®¤ å®à¤ § ª«îç ¥âáï ¢â®¬, çâ® § 票¥ xn+1 ¥áâì ¡áæ¨áá â®çª¨ ¯¥à¥á¥ç¥¨ï ¯àאַ©, ¯à®å®¤ï饩 ç¥à¥§ â®çª¨ (x0; f(x0 )) ¨ (xn ; f(xn )), á ®áìîOx, â® ¥áâì ¨§ â®çª¨ (x0; f(x0 )) ¯à®¢®¤¨âáï ᥬ¥©á⢮ å®à¤£à 䨪 äãªæ¨¨ f(x) (à¨á. 4.7).
묨 á«®¢ ¬¨, ª ¦¤®¬è £¥ § ¯à¨¡«¨¦¥®¥ § 票¥ xn+1 ¯à¨¨¬ ¥âáï ª®à¥ì ¨â¥à¯®«ï樮®£® ¬®£®ç«¥ ¯¥à¢®© á⥯¥¨, ¯®áâ஥®£®¯® § ç¥¨ï¬ f(x) ¢ â®çª å x0 ¨ xn. ¬¥® ¯®í⮬㠤 멬¥â®¤ ¨®£¤ §ë¢ îâ ¬¥â®¤®¬ «¨¥©®© ¨â¥à¯®«ï樨.ਠ¯¯à®ªá¨¬ 樨 ¢ ¬¥â®¤¥ ìîâ® ¯à®¨§¢®¤®© f 0 (xn)n 1 ) ¯®«ãç ¥âª®¥ç®-à §®áâë¬ ®â®è¥¨¥¬ f(xxn ) f(xn xn 1áï ¬¥â®¤ ᥪãé¨å:n 1 f(x );xn+1 = xn f(xxn) xf(xn = 1; 2; : : :) nnn1â®â ¬¥â®¤ ®â«¨ç ¥âáï ®â à ¥¥ ¨§ãç¥ëå ⥬, çâ® ª ¦¤®¬ è £¥ ¤«ï 宦¤¥¨ï xn+1 ¨á¯®«ì§ã¥âáï ¥ ⮫쪮§ 票¥ xn , ® ¨ § 票¥ xn 1. ¥â®¤ë, ®¡« ¤ î騥 â ª¨¬á¢®©á⢮¬, §ë¢ îâáï ¤¢ãåè £®¢ë¬¨.
¨ âॡãîâ § ¤ ¨ï¤¢ãå ç «ìëå ¯à¨¡«¨¦¥¨©: x0 ¨ x1.⬥⨬ ¥é¥ ®¤ã «î¡®¯ëâãî ®á®¡¥®áâì ¬¥â®¤ ᥪãé¨å: ¥£® ¯®à冷ª á室¨¬®á⨠(á¬. ä®à¬ã«ã (4.6)) ¥áâì ¨àà æ¨® «ì®¥ ç¨á«® k 1,6180, ïî饥áï ¯®«®¦¨â¥«ì묪®à¥¬ ãà ¢¥¨ï k2 k 1 = 0 ¨ §ë¢ ¥¬®¥ §®«®âë¬ á¥ç¥¨¥¬. â® ç¨á«® ¨¬¥¥â ¢ ¦®¥ § 票¥ ¢ ⥮ਨ ç¨á¥«¨¡® çç¨.89®â஫ì â®ç®á⨠¢ à áᬠâਢ ¥¬®¬ ¬¥â®¤¥ ¬®¦¥â¡ëâì ®áãé¥á⢫¥ á ¯®¬®éìî ä®à¬ã«ë (4.16).¥®¬¥âà¨ç¥áª¨ ¬¥â®¤ ᥪãé¨å á®á⮨⠢ ⮬, çâ® ç¥à¥§â®çª¨ (xn 1; f(xn 1 )) ¨ (xn ; f(xn )) ¯à®¢®¤¨âáï ¯àï¬ ï, ¡áæ¨áá â®çª¨ ¯¥à¥á¥ç¥¨ï ª®â®à®© á ®áìî Ox ï¥âáï®¢ë¬ ¯à¨¡«¨¦¥¨¥¬ xn+1 (à¨á.
4.8). ।¥«®¬ ¯®áâ஥®£®á¥¬¥©á⢠ᥪãé¨å ï¥âáï ª á ⥫ì ï ª £à 䨪ã äãªæ¨¨f(x) ¢ â®çª¥ x . ¬¥â¨¬, çâ® ¢ ®á®¢¥ ¬¥â®¤ ᥪãé¨å, ª ª¨ ¬¥â®¤ å®à¤, «¥¦¨â ¨¤¥ï «¨¥©®© ¨â¥à¯®«ï樨.¨á. 4.8. ¥â®¤ ᥪãé¨å4.3.4. ਢ¥¤¥¬ à §à ¡®â ë© ..¥¡ëè¥¢ë¬ «£®à¨â¬ ¯®áâ஥¨ï ¨â¥à 樮ëå ¬¥â®¤®¢, ¨¬¥îé¨å ᪮«ì 㣮¤® ¢ë᮪¨© ¯®à冷ª á室¨¬®áâ¨. ®á®¢¥ í⮣® «£®à¨â¬ «¥¦¨âà §«®¦¥¨¥ ¢ àï¤ ¥©«®à äãªæ¨¨, ®¡à ⮩ ª äãªæ¨¨f(x).ãáâì ãà ¢¥¨¥ (4.1) ¨¬¥¥â ®â१ª¥ [a; b] ¥¤¨áâ¢¥ë© ª®à¥ì x, ¯à¨ç¥¬ äãªæ¨ï y = f(x) í⮬ ®â१ª¥¤®áâ â®ç® £« ¤ª ï ¨ áâண® ¬®®â® ï (¯®á«¥¤¥¥ ®§ ç ¥â, çâ® f 0 (x) 6= 0, â.
¥. [a; b] ®¤®§ ç® ®â®¡à ¦ ¥âáï ¢ ¥ª®â®àë© ®â१®ª [c; d]). ®£¤ áãé¥áâ¢ã¥â äãªæ¨ï x = g(y),®¡à â ï ª y = f(x), ®¯à¥¤¥«¥ ï [c; d] ¨ ¨¬¥îé ï â ª®© ¦¥ ¯®à冷ª £« ¤ª®áâ¨, ª ª f(x). 祢¨¤®, ¨¬¥¥â ¬¥áâ®à ¢¥á⢮ x g[f(x)], ¯®á«¥¤®¢ ⥫쮥 ¤¨ää¥à¥æ¨à®¢ ¨¥90ª®â®à®£® ¤ ¥â ¬ á¨á⥬㠫¨¥©ëå ãà ¢¥¨© ¤«ï 宦¤¥¨ï ¯à®¨§¢®¤ëå äãªæ¨¨ g(y), ¯à¨ç¥¬ ¬ âà¨æ í⮩ á¨áâ¥¬ë ¨¬¥¥â âà¥ã£®«ìë© ¢¨¤:g0 [f(x)]f 0 (x) = 1;g0 [f(x)]f 00 (x) + g00[f(x)](f 0 (x))2 = 0;(4:17)00000000000003g [f(x)]f (x) + 3g [f(x)]f (x)f (x) + g [f(x)](f (x)) = 0 âáî¤ á«¥¤ã¥â, çâ®1 ;g0 [f(x)] = f 0 (x)00 (x)g00[f(x)] = (ff0 (x))3¨ â.
¤.à¨áâã¯ ï ¥¯®á।á⢥® ª ®¯¨á ¨î «£®à¨â¬ ¥¡ë襢 , § ¬¥â¨¬, çâ® x = g(0). áᬮâਬ ¯à®¨§¢®«ìãî â®çªã y 2 [c; d]. ®£« á® ä®à¬ã«¥ ¥©«®à ,r(k )(r +1)X() yr+1g(0) = g(y) + ( 1)k g k!(y) yk + ( 1)r+1 g(r + 1)!k=1( «¥¦¨â ¬¥¦¤ã 0 ¨ y). ¥à¥å®¤ï ª ¯¥à¥¬¥®© x, ¯®«ã稬r(k )Xk + ( 1)r+1 g(r+1) () f(x)r+1;f(x)x=x+ ( 1)k g [f(x)]k!(r + 1)!k=1(4:18)¯à¨ç¥¬ ¯à®¨§¢®¤ë¥ äãªæ¨¨ g[f(x)] ¬®£ãâ ¡ëâì ©¤¥ë ¨§á¨á⥬ë (4.17).¢¥¤¥¬ ®¡®§ 票¥r(k )Xk :f(x)r (x) = x + ( 1)k g [f(x)]k!k=1®£¤ , ®ç¥¢¨¤®, ãà ¢¥¨¥x = r (x)¨¬¥¥â ª®à¥ì x . ஬¥ ⮣®,(rl) (x ) = 0; l = 1; 2; : : :; r: ª¨¬ ®¡à §®¬, ¨â¥à æ¨®ë© ¬¥â®¤91(4:19)xn+1 = r (xn);n = 0; 1; : : :;¢á«¥¤á⢨¥ ⥮६ë 4.5 ¨¬¥¥â (r + 1)-© ¯®à冷ª á室¨¬®áâ¨. ¤ ç 4.4.®ª § âì à ¢¥á⢮ (4.19). ¬¥â¨¬, çâ® à¥è¥¨¥ § ¤ ç¨ 4.4 âॡã¥â ¢¥áì¬ £à®¬®§¤ª¨å ¢ëª« ¤®ª, ¯®í⮬㠯®à冷ª á室¨¬®á⨠¬¥â®¤ ¯à®é¥ ©â¨ ¥¯®á।á⢥®, â.
¥. ¡¥§ ¨á¯®«ì§®¢ ¨ï ⥮६ë 4.5.«ï í⮣® ¯®¤áâ ¢¨¬ ¢ (4.18) x = xn 1. ®£¤ (r +1)r+1x xn = ( 1)r+1 g (r +[f()]1)! f(xn 1 ) ;£¤¥ «¥¦¨â ¬¥¦¤ã x ¨ xn 1. ãáâì L = xmaxjf 0 (x)j,2[a; b]Mr+1 = xmaxjg(r+1) [f(x)]j. ª ª ª2[a; b]jf(xn 1)j = jf(xn 1) f(x )j = jf 0 ()jjxnâ®r+1jxn x j M(rr+1+L1)! jxn M Lr r+1+1r1+( +1)+( +1)2 +(r + 1)!r M Lrr= (r + 1)! jx x j+1n( +1)+1r01x j;1xjr+1 1:::+(r+1)nrx j Ljxn11jx0 xj(r+1)n =jx0 x jrnrr( +1) (1)+1:r+1â ª, ¥á«¨ jx0 xj < 1 ¨ M(rr+1+L1)! jx0 x j = ! < 1, ⮨¬¥¥â ¬¥áâ® ®æ¥ª jxn x j ! rn( +1)r1;㪠§ë¢ îé ï ®ç¥ì ¡ëáâàãî á室¨¬®áâì ¬¥â®¤ .