~ISLOWOJ RQD NAZYWA@T SHODQ]IMSQ, ESLI ON IMEET SUMMU (W \TOM SLU^AE SU]ESTWUET KONE^NYJ PREDEL POSLEDOWATELXNOSTI ^ASTI^NYH
SUMM RQDA) I RASHODQ]IMSQ, |
ESLI TAKOWAQ NE SU]ESTWUET ( lim Sn NE |
SU]ESTWUET). eSLI ^ISLOWOJ RQD SHODITSQ, |
n!1 |
TO, ESTESTWENNO, ON IMEET |
SUMMU. |
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1: nAJTI SUMMU RQDA |
X |
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9n2 + 3n |
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n=1 |
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zAPI[EM OB]IJ ^LEN RQDA W WIDE RAZNOSTI DWUH DROBEJ (\TO LEG- KO SDELATX, ISPOLXZUQ RAZLOVENIE DROBI NA PROSTEJ[IE SLAGAEMYE I
METOD NEOPREDELENNYH KO\FFICIENTOW) |
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un = |
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9n2 + 3n ; 2 |
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(3n ; 1)(3n + 2) |
3n ; 1 |
3n + 2 |
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I WYPI[EM NESKOLXKO ^LENOW RQDA |
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u1 = |
2 ; 5 |
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= 5 |
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u3 |
= 8 |
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u4 = |
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::: |
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un;1 = |
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un = |
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3n ; 4 ; 3n ; 1 |
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3n ; 1 ; 3n + 2 |
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sOSTAWIM WYRAVENIE DLQ n; OJ ^ASTI^NOJ SUMMY |
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Sn = u1 + u2 + : : : + un;1 + un = |
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= 2 ;5 |
+ 5 |
;8 + |
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+: : :+ |
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3n;4 |
3n;1 |
3n;1 |
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3n+2 |
wIDNO, ^TO W REZULXTATE SLOVENIQ OSTANUTSQ TOLXKO PERWOE I POSLED- |
NEE SLAGAEMYE |
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Sn = |
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tOGDA SUMMA RQDA |
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3n + 2 |
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S = lim Sn |
= lim |
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2 ; 3n + 2! |
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n!1 |
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n!1 |
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2 n |
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2: |
nAJTI SUMMU RQDA |
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X |
5! |
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n=1 |
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sUMMU TAKOGO RQDA |
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S = |
5 + |
5! + |
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5! |
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+ ::: + |
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+ ::: |
MOVNO RASSMATRIWATX KAK SUMMU BESKONE^NO UBYWA@]EJ GEOMET- |
RI^ESKOJ PROGRESSII |
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q + q2 + q3 + q4 + ::: +n +::: |
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SO ZNAMENATELEM q = 2 |
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5 |
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b1 |
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2=5 |
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= 2 |
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nAHODIM SUMMU PO IZWESTNOJ FORMULE |
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S = |
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= |
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1 ; q |
1 ; 2=5 |
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154 |
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3 |
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tAKIM OBRAZOM, RE[ITX WOPROS O SHODIMOSTI RQDA MOVNO PUTEM NE- POSREDSTWENNOGO NAHOVDENIQ ZNA^ENIQ SUMMY RQDA. nO W BOLX[IN- STWE SLU^AEW \TA ZADA^A POWY[ENNOJ SLOVNOSTI I RE[AETSQ LI[X W NEKOTORYH ^ASTNYH SLU^AQH, KOGDA UDAETSQ SOSTAWITX KOMPAKTNOE WYRAVENIE DLQ n; OJ ^ASTI^NOJ SUMMY S CELX@ POSLEDU@]EGO NA- HOVDENIQ EE PREDELA.
zNA^ITELXNO BOLEE PROSTO WOPROS O SHODIMOSTI ILI RASHODIMOSTI ^ISLOWOGO RQDA, A ZNA^IT I WOPROS O SU]ESTWOWANII EGO SUMMY, RE- [AETSQ S POMO]X@ DRUGIH DOSTATO^NYH PRIZNAKOW SHODIMOSTI. rAS- SMOTRIM SNA^ALA WAVNYE PONQTIQ I SWOJSTWA RQDOW.
o P R E D E L E N I E. oSTATKOM RQDA POSLE n; GO ^LENA NAZYWA- @T RQD, POLU^ENNYJ IZ DANNOGO PUTEM OTBRASYWANIQ EGO n PERWYH
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^LENOW Rn = un+1 + un+2 + ::: = |
1 uk : |
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k=n+1 |
tOGDA SUMMA RQDA MOVET BYTX ZAPISANA WYRAVENIEM
S = u1 + u2 + ::: + un + un+1 + un+2 + ::: = Sn + Rn:
tAK KAK SUMMA PERWYH n ^LENOW RQDA WSEGDA ESTX KONE^NOE ^ISLO, TO SHODIMOSTX RQDA OPREDELQETSQ SHODIMOSTX@ EGO OSTATKA. oSTATOK RQDA Rn = S ;Sn ESTX RAZNOSTX MEVDU SUMMOJ WSEGO RQDA I SUMMOJ n EGO PERWYH ^LENOW. pO\TOMU OSTATOK RQDA PO ABSOL@TNOJ WELI^I- NE POKAZYWAET, KAKU@ O[IBKU MY DOPUSKAEM PRI ZAMENE SUMMY RQDA SUMMOJ KONE^NOGO ^ISLA PERWYH EGO ^LENOW.
sWOJSTWA SHODQ]IHSQ ^ISLOWYH RQDOW
1.rQD I EGO OSTATOK LIBO ODNOWREMENNO SHODQTSQ, LIBO RASHODQT- SQ. oSTATOK SHODQ]EGOSQ RQDA STREMITSQ K NUL@.
2.sHODQ]IESQ RQDY MOVNO PO^LENNO SKLADYWATX, WY^ITATX, UM- NOVATX WSE ^LENY SHODQ]EGOSQ RQDA NA POSTOQNNOE ^ISLO, PEREMNO- VATX RQDY KAK DWA MNOGO^LENA, I PRI \TOM POLU^ENNYE RQDY BUDUT QWLQTXSQ SHODQ]IMISQ, A IH SUMMY PRINIMA@T U^ASTIE W ANALOGI^-
NYH ARIFMETI^ESKIH OPERACIQH.
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an = a1 + a2 + ::: |
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bn = b1 |
+ b2 + :::; |
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E |
ESLI |
1 |
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n=1 |
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n=1 |
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DWA SHODQ]IHSQ ^ISLOWYH RQDA, IME@]IH SUMMY A I B TO |
X |
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a) 1 an |
1 bn = A B: b) |
1 an = A: c) |
1 an |
1 bn = A B: |
n=1 |
n=1 |
n=1 |
n=1 |
n=1 |
1.2. nEOBHODIMYJ PRIZNAK SHODIMOSTI
eSLI ^ISLOWOJ RQD 1 un SHODITSQ, TO PREDEL EGO OB]EGO ^LENA OBQ-
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n=1 |
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lim un = 0: |
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ZATELXNO RAWEN NUL@, T.E. |
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n!1 |
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pRIWEDENNYJ PRIZNAK SHODIMOSTI SLEDUET PONIMATX TAK: |
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eSLI |
lim un |
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TO RQD |
1 |
un |
RASHODITSQ TO^NO |
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NO |
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6 |
= 0 |
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n!1 |
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n=1 |
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ESLI |
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lim un = 0, TO RQD |
1 un MOVET SHODITXSQ, |
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n=1 |
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!1 |
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NO MOVET I RASHODITXSQ. |
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tAK, NAPRIMER: |
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1) |
1 1 = 1 + 1 + ::: + 1 + ::: |
RASHODITSQ, T.K. lim 1 = 1 |
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=0 |
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n=1 |
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n |
!1 |
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2) n1=0(;1)n = 1 |
; 1 + 1 ; ::: |
RASHODITSQ, T.K. nlim!1(;1)n |
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NE SU]ESTWUET. |
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3) |
1 2n ; 1 |
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+ 3 + |
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+:::: RASHODITSQ, T.K. lim |
2n ; |
1 = |
2 |
6 |
=:0 |
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n=1 3n + 1 |
4 7 10 |
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n!1 |
3n + 1 3 |
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+ 1 + |
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1 |
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4) |
1 |
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+ :::: |
RASHODITSQ, HOTQ |
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lim |
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= 0: |
n=1 3n + 1 |
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4 7 10 |
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n!1 |
3n + 1 |
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X |
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fAKT RASHODIMOSTI RQDA PRI WYPOLNENII NEOBHODIMOGO PRIZNAKA SHODIMOSTI GOWORIT O TOM, ^TO DLQ SHODIMOSTI RQDA KROME UBYWANIQ I STREMLENIQ K NUL@ OB]EGO ^LENA RQDA NUVNA DOSTATO^NAQ SKOROSTX UBYWANIQ ^LENOW RQDA, ^TOBY NE PROISHODILO "KATASTROFI^ESKOE" NAKOPLENIE ^ASTI^NOJ SUMMY RQDA. oTWET NA \TI WOPROSY DA@T, TAK NAZYWAEMYE, DOSTATO^NYE PRIZNAKI SHODIMOSTI ^ISLOWYH RQDOW, KO- TORYE NIVE BUDUT RASSMOTRENY POROZNX DLQ ZNAKOPOLOVITELXNYH I ZNAKOPEREMENNYH RQDOW.
1.3. dOSTATO^NYE PRIZNAKI SHODIMOSTI ZNAKOPOLOVITELX- NYH RQDOW
~ISLOWOJ RQD QWLQETSQ ZNAKOPOLOVITELXNYM, ESLI WSE EGO ^LENY POLOVITELXNY. pRIWEDEM NESKOLXKO DOSTATO^NYH PRIZNAKOW SHODI- MOSTI ZNAKOPOLOVITELXNYH RQDOW, KAVDYJ IZ KOTORYH UDOBNO IS- POLXZOWATX W SOOTWETSTWU@]IH SLU^AQH.
n > N. tOGDA
1.3.1. pRIZNAK SRAWNENIQ 1
pUSTX DANY DWA ZNAKOPOLOVITELXNYH RQDA |
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1 un = u1 + u2 + u3 + ::: + un + ::: |
(1) |
n=1 |
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X |
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1 vn = v1 + v2 + v3 + ::: + vn + ::: |
(2) |
nX=1
PRI^EM ^LENY RQDA (1) NE PREWOSHODQT SOOTWETSTWU@]IH ^LENOW RQDA
(2) PO KRAJNEJ MERE, NA^INAQ S NEKOTOROGO NOMERA n = N T.E. un vn DLQ WSEH
IZ SHODIMOSTI RQDA (2) WSEGDA SLEDUET SHODIMOSTX I RQDA (1), IZ RASHODIMOSTI RQDA (1) SLEDUET I RASHODIMOSTX RQDA (2).
iNYMI SLOWAMI: ESLI ^LENY NEKOTOROGO ZNAKOPOLOVITELXNOGO RQ- DA MENX[E SOOTWETSTWU@]IH ^LENOW SHODQ]EGO ZNAKOPOLOVITELXNO- GO RQDA, TO ISHODNYJ RQD SHODITSQ, A ESLI ^LENY NEKOTOROGO ZNAKOPO- LOVITELXNOGO RQDA BOLX[E SOOTWETSTWU@]IH ^LENOW RASHODQ]EGOSQ ZNAKOPOLOVITELXNOGO RQDA, TO ISHODNYJ RQD RASHODITSQ.
1.3.2. pRIZNAK SRAWNENIQ 2 (PREDELXNYJ)
eSLI SU]ESTWUET KONE^NYJ, OTLI^NYJ OT NULQ PREDEL OTNO[ENIQ
nlim un = A 6= 0TO OBA RQDA (1) I (2) ODNOWREMENNO LIBO SHODQTSQ,
!1 vn
LIBO RASHODQTSQ.
pRI PRIMENENII PRIZNAKA SRAWNENIQ DANNYJ RQD SOPOSTAWLQETSQ S ODNIM IZ, TAK NAZYWAEMYH, \TALONNYH RQDOW, SHODIMOSTX ILI RASHO- DIMOSTX KOTORYH USTANOWLENA.
|TALONNYE RQDY
1) |
gEOMETRI^ESKIJ RQD |
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1 qn : |
8 |
PRI |
jqj < 1 |
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nX=1 |
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; RQD RASHODITSQ |
oBOB]ENNYJ GARMONI^ESKIJ RQD |
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> 1 RQD SHODITSQ |
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1 RQD RASHODITSQ: |
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w ^ASTNOSTI |
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k=1 |
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PRI |
POLU^AEM |
3) |
gARMONI^ESKIJ RQD |
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= 1 + 2 + 3 + : : : + n + : : : ; RASHODITSQ |
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sUTX ISPOLXZOWANIQ PRIZNAKA SRAWNENIQ, OSOBENNO EGO PREDELXNOJ FORMY, SOSTOIT W TOM, ^TO NUVNO DLQ DANNOGO RQDA ORGANIZOWATX \KWIWALENTNYJ EMU RQD W WIDE ODNOGO IZ \TALONNYH RQDOW I SDELATX WYWOD O SHODIMOSTI. |KWIWALENTNOSTX DANNOGO I SOSTAWLENNOGO RQ- DOW ZDESX SLEDUET PONIMATX KAK PRIBLIVENNOE RAWENSTWO ^LENOW RQ- DA, NA^INAQ S KAKOGO-TO DOSTATO^NO BOLX[OGO NOMERA.
pRIZNAK SRAWNENIQ PROST W ISPOLNENII I O^ENX \FFEKTIWEN, NO, K SOVALENI@, NE WSEGDA MOVET BYTX ISPOLXZOWAN. pO\TOMU NEOBHODIMY I DRUGIE DOSTATO^NYE PRIZNAKI.
1.3.3. pRIZNAK dALAMBERA
eSLI W ^ISLOWOM ZNAKOPOLOVITELXNOM RQDE 1 un |
SU]ESTWUET |
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n=1 |
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PREDEL OTNO[ENIQ POSLEDU@]EGO ^LENA RQDA un+1 K PREDYDU]EMU un |
PRI n ! 1 RAWNYJ ^ISLU p : |
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un+1 |
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TO 8 |
ESLI |
p < 1 |
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RQD SHODITSQ |
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lim |
= p |
ESLI |
p > 1 |
RQD RASHODITSQ |
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un |
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PRIZNAK NE RABOTAET: |
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sMYSL PRIZNAKA dALAMBERA SOSTOIT W TOM |
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^TO ^LENY ^ISLOWOGO RQ |
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DA S DOSTATO^NO BOLX[IMI NOMERAMI DOLVNY W SLU^AE SHODIMOSTI RQDA WESTI SEBQ KAK ^LENY BESKONE^NO UBYWA@]EJ GEOMETRI^ESKOJ PROGRESSII, T.E. KAVDYJ SLEDU@]IJ ^LEN RQDA DOLVEN BYTX W p > 1 RAZ MENX[E PREDYDU]EGO.
1.3.4.rADIKALXNYJ PRIZNAK kO[I
eSLI W ^ISLOWOM ZNAKOPOLOVITELXNOM RQDE 1 un |
SU]ESTWUET |
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PREDEL KORNQ n; OJ STEPENI IZ OB]EGO ^LENA RQDA |
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ESLI |
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RQD SHODITSQ |
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nlim p |
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ESLI |
q > 1 |
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RQD RASHODITSQ |
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un |
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PRIZNAK NE RABOTAET: |
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sMYSL RADIKALXNOGO PRIZNAKA kO[I SOSTOIT W TOM |
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^TO ^LENY ^I |
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SLOWOGO RQDA S DOSTATO^NO BOLX[IMI NOMERAMI DOLVNY W SLU^AE SHODIMOSTI RQDA WESTI SEBQ KAK ^LENY SHODQ]EGOSQ GEOMETRI^ESKOGO RQDA.
Z1f(x) dx
1
TO RQD
1.3.5.iNTEGRALXNYJ PRIZNAK kO[I
eSLI f(x) PRI x 1 ESTX NEPRERYWNAQ, POLOVITELXNAQ I MONO- TONNO UBYWA@]AQ FUNKCIQ TAKAQ, ^TO PRI NATURALXNYH ZNA^ENIQH
ARGUMENTA ZNA^ENIQ FUNKCII SOWPADA@T SO ZNA^ENIQMI ^LENOW RQ-
1
DA X un T.E. u1 = f(1) u2 = f(2) : : : un = f(n)
n=1
1 n SHODITSQ ESLI SHODITSQ NESOBSTWENNYJ INTEGRAL
X u ,
n=1
I RASHODITSQ, ESLI \TOT INTEGRAL RASHODITSQ.
~TOBY SOSTAWITX PODYNTEGRALXNU@ FUNKCI@ DOSTATO^NO ZAME- NITX W WYRAVENII OB]EGO ^LENA RQDA n NA x.
iSPOLXZOWANIE DANNOGO PRIZNAKA SWQZANO S ISSLEDOWANIEM NA SHO- DIMOSTX NESOBSTWENNOGO INTEGRALA, ^TO NE WSEGDA QWLQETSQ PROSTOJ ZADA^EJ, PO\TOMU PRIZNAK ISPOLXZU@T TOLXKO W TEH SLU^AQH, KOGDA OSTALXNYE BESSILXNY.
1.4. pRIMERY ISSLEDOWANIQ ZNAKOPOLOVITELXNYH RQDOW NA SHODIMOSTX
pRIZNAK SRAWNENIQ
pRIMENQETSQ DLQ RE[ENIQ WOPROSA O SHODIMOSTI, K PRIMERU, RQDOW |
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+ 3n + 1 |
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+ 2 |
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pn7 + 4n5 |
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n=1 sin p5 |
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arctgn4 |
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w \TIH SLU^AQH MOVNO ISPOLXZOWATX PRIEM WYDELENIQ GLAWNYH ^LE-
NOW W WYRAVENII DLQ OB]EGO ^LENA RQDA, ZAMENU BESKONE^NO MALYH
WELI^IN \KWIWALENTNYMI I DR., |
^TOBY PRIWESTI DANNYJ RQD K \K- |
WIWALENTNOMU RQDU WIDA |
1 A |
ILI |
1 |
A q |
n |
I SDELATX WYWOD O |
n=1 |
nk |
n=1 |
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SHODIMOSTI. |
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tABLICA \KWIWALENTNYH BESKONE^NO MALYH WELI^IN (x) ! 0
sin (x) (x) tg (x) (x) e (x) ; 1 (x)
arcsin (x) (x)
arctg (x) (x) qn 1 + (x) ; 1 (nx) :
1 ; cos (x) 2(x)
2
ln(1 + (x)) (x)
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1 |
1 + 2n |
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8: |
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{ RQD RASHODITSQ, TAK KAK ^LENY EGO DLQ DOSTATO^NO |
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1 + n2 |
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BOLX[IH n \KWIWALENTNY ^LENAM GARMONI^ESKOGO RQDA |
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1 + 2n |
2n |
2 |
1 2 |
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n A RQD |
X |
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RASHODITSQ. |
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wOOB]E, ESLI PONIMATX ZDESX SIMWOL \KWIWALENTNOSTI " " KAK ODINAKOWOE POWEDENIE RQDOW W SMYSLE SHODIMOSTI I RASHODIMOSTI,
TO MOVNO POLXZOWATXSQ KRATKOJ ZAPISX@ |
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1 + 2n |
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{ RQD RASHODITSQ. |
n=1 |
1 + n2 |
n=1 |
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9: |
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2n ; |
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RQD SHODITSQ KAK |
n=1 |
n (1 + n) (n + 2) |
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n3 |
n2 |
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OBOB]ENNYJ GARMONI^ESKIJ RQD S POKAZATELEM k = 2 > 1. |
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1 |
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RQD RASHODITSQ KAK OBOB]ENNYJ |
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n2=3 |
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n=1 |
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+ 4n |
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GARMONI^ESKIJ RQD S POKAZATELEM k = 2=3 < 1. |
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11: |
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sin |
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2p |
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n=1 |
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SQ KAK OBOB]ENNYJ GARMONI^ESKIJ RQD S POKAZATELEM k = 3=2 > 1. |
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zDESX ISPOLXZOWANO TO, ^TO |
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2p |
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PRI n ! 1: |
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n |
n |
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12: |
1 |
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n arctg |
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RQD SHODITSQ KAK |
n=1 |
n4 |
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n4 |
n=1 |
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OBOB]ENNYJ GARMONI^ESKIJ RQD S POKAZATELEM k = 3 > 1. |
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zDESX ISPOLXZOWANA \KWIWALENTNOSTX arctg |
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PRI n ! 1: |
n4 |
n4 |
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13: |
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; RQD RASHODITSQ. w DANNOM SLU- |
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^AE ISPOLXZOWANO TO OBSTOQTELXSTWO, ^TO cos |
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n |
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1 sin |
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14: |
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= |
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RQD SHODITSQ KAK GEOMET- |
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2n |
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2n |
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n=1 |
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n=1 |
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n=1 |
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RI^ESKIJ SO ZNAMENATELEM q = 1=2 < 1: zDESX ISPOLXZOWANA \KWIWA- |
LENTNOSTX sin |
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PRI n ! 1: |
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2n |
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RASHODITSQ KAK OBOB]ENNYJ GARMONI^ESKIJ RQD S PO-
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53n |
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15: |
1 |
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e;2n |
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RQD RASHODITSQ KAK |
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n=1 |
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n=1 |
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n=1 |
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GEOMETRI^ESKIJ SO ZNAMENATELEM |
q = 125e2 |
> 1: |
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1 |
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16: |
1 |
; cos n2 |
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; |
RQD SHODITSQ KAK OBOB]ENNYJ |
1 |
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1 2n4 |
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n=1 |
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n=1 |
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GARMONI^ESKIJ RQD S POKAZATELEM k = 4 > 1. zDESX MY WOSPOLXZOWA- |
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1 |
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(1=n2)2 |
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LISX TEM, ^TO PRI n ! 1 : |
1 ; cos |
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= |
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n2 |
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2n4 |
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17: |
1 ln |
01 + pn1 |
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pn |
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2 |
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n1=2 |
; |
RQD RASHODIT- |
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n=1 |
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n=1 |
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SQ KAK OBOB]ENNYJ GARMONI^ESKIJ S POKAZATELEM k = 1=2 < 1: |
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ln 01 + |
2 |
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zDESX ISPOLXZOWANO |
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p |
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PRI n ! 1. |
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arctgn2 |
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n2 + 2n + 7: |
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18: 1 |
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n=1 |
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iZWESTNO, ^TO PRI PRI n ! 1 IMEET MESTO NERAWENSTWO arctg1 <=2 \TO ZNA^IT, ^TO ^ISLITELX ISHODNOJ DROBI ESTX WELI^INA OGRA- NI^ENNAQ, PO\TOMU MOVNO ZAPISATX
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arctgn2 |
< |
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n + 2n + 7 |
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rQD |
1 |
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SHODITSQ KAK OBOB]ENNYJ GARMONI^ESKIJ RQD S PO- |
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n2 |
nX=1
KAZATELEM k = 2 > 1 A ZNA^IT SHODITSQ I ISHODNYJ RQD.
1arcin2n
19: nX=1 p4 n3 + 3n + 1:
zNA^ENIQ arcin2n 2 [0 2=4] PO\TOMU ^ISLITELX ISHODNOJ DROBI ESTX NEKOTOROE ^ISLO A I ISHODNYJ RQD BUDET WESTI SEBQ TAKVE, KAK RQD
1 |
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1 A |
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n=1 n3=4 |
n=1 pn3 + 3n + 1 |
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1 A
rQD X n3=4
n=1
KAZATELEM k = 3=4 < 1 A ZNA^IT RASHODITSQ I ISHODNYJ RQD.
pRIZNAK dALAMBERA
pRIMENQETSQ DLQ RE[ENIQ WOPROSA O SHODIMOSTI TAKIH RQDOW, OB- ]IE ^LENY KOTORYH SODERVAT STEPENNYE, POKAZATELXNYE WYRAVENIQ
I FAKTORIALY |
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1 2n |
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1 (n + 5)2 |
1 n! |
1 nn |
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1 (n + 1)! + (n + 2)! |
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3 |
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pRIMENQQ PRIZNAK dALAMBERA, NEOBHODIMO: |
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a) ZAPISATX (n + 1); YJ ^LEN RQDA un+1 DLQ ^EGO W WYRAVENII |
DLQ OB]EGO ^LENA un ZAMENITX n NA (n + 1) |
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b) |
NAJTI PREDEL OTNO[ENIQ |
lim |
un+1 = p |
SRAWNITX POLU- |
^ENNOE ZNA^ENIE p |
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un |
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S EDINICEJ I SDELATX WYWOD O SHODIMOSTI RQDA |
(NAPOMNIM, ^TO PRI p < 1 RQD SHODITSQ, A PRI p > 1 RQD RASHODITSQ.)
zAME^ANIE. pRI PRIMENENII PRIZNAKA dALAMBERA (A TAKVE RADI- KALXNOGO PRIZNAKA kO[I) MOVET WSTRETITXSQ NEOBHODIMOSTX ISPOLX- ZOWANIQ WTOROGO ZAME^ATELXNOGO PREDELA. nAPOMNIM EGO
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; n |
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n!1 |
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20: |
1 |
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5n |
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un+1 = |
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5n+1 |
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(2n + 1)2 |
(2n + 1)2 |
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n=1 |
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5n+1 |
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5(2n + 1)2 |
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lim |
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= 5 > 1 |
un |
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{ RQD RASHODITSQ. |
zDESX U^TENO, ^TO |
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lim |
= 1: |
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p |
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n!1 (2n + 3)2 |
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21: |
1 |
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3n + 2 |
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n! |
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n=1 |
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X p |
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un+1 = q |
3(n + 1) + 2 |
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3n + 2 |
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3n + 5 |
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un = |
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n! |
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p |
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lim |
un+1 = lim |
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n! |
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3n + 5 |
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(n + 1)! |
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n!1 |
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n!1 n!(n + 1)p3n + 2 |
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{ RQD SHODITSQ. |
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n!1 p3n + 2 (n + 1) |
n!1 n + 1 |
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p |
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1 |
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zDESX U^TENO, ^TO PRI n ! 1 p3n + 2 |
! 1 |
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! 0: |
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n + 1 |
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