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Сборник задач по высшей математике 2 том

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6.9.3.

3a,L1;aHa <PYHKIJ;IUI paCnpe,ll;eJIeHHjf H. C. B. X

 

O'

x < -11",

 

F(x) = { a(cosx + c),

-11" :::;; X :::;; 0,

 

1,

0< x.

Hat!:TH:

a) 3HaqeHHjf nOCTOjfHHbIX a H C;

6)f(x);

B) P1 {X E [- ~, ~]}, P2 { X = 2;03}.

6.9.4.CJIyqai\HM BeJIHqHHa X 3a,L1;aHa <PYHKIJ;Hei\ pacnpe,ll;eJIeHHjf

O'

x :::;;A,

F(x) = { ~v'X- 1,

A<x:::;;B,

1,

B <x.

Hai\TH: 3HaqeHHjf A H B, nJIOTHOCTb pacnpe,ll;eJIeHHjf H. c. B. X,

BepOjfTHOCTb C06blTHjf C = {X E (3; 5)}.

6.9.5. IIpH KaKOM 3HaqeHHH napaMeTpa C <PYHKIJ;Hjf

 

 

 

f(x) = {xS'X

~ 1,

 

 

 

 

 

 

 

 

0,

x < 1

 

 

 

 

 

 

MO:>KeT 6bITb nJIOTHOCTbIO pacnpe,ll;eJIeHHjf HeKoTopoi\ HenpepbIB-

 

HOi\ c. B. X? Hai\TH P{1 < X < 5}.

 

 

 

 

 

Q OqeBH,ll;HO, 'ITOf(x)

> °npH C > 0,

 

lim

f(x) = 0.

lknoJIb3Yjf CBOi\-

 

 

 

00

x-+±oo

 

 

 

 

 

CTBO HOpMHpOBaHHOCTH (

f f(x) dx = 1), Hai\,ll;eM 3HaqeHHe napaMeTpa C:

 

 

 

 

- 00

 

 

 

 

 

 

 

00

1

 

00

 

b

 

 

 

 

 

f

f(x) dx = f

°dx + f ~ dx = b~~ f x-4 dx =

 

 

 

- 00

- 00

 

1

 

1

lib = _ C (0 -1) = C,

 

 

 

 

= _C . lim

 

 

 

 

 

3

b-+oo x 3 1

 

3

3

 

T. e. ~ = 1, OTCIO,ll;a C = 3. TaKHM o6pa30M, <PYHKIJ;Hjf

 

 

 

 

 

 

 

3 ,

X

~ 1,

 

 

 

 

 

 

 

 

f(x) = { x4

x < 1

 

 

 

 

 

 

 

 

0,

 

 

 

 

 

jfBJIjfeTCjf nJIOTHOCTbIO pacnpe,ll;eJIeHHjf HeKoTopoi\ c. B. X.

 

 

 

Hai\,ll;eM HCKOMYIO BepOjfTHOCTb, HCnOJIb3Yjf <POPMYJIY

 

 

 

 

 

 

 

 

b

 

 

 

 

 

 

 

P{a:::;;X:::;;b}=

ff(x)dx.

 

 

 

 

IIoJIyqaeM:

 

5

a

 

 

 

 

 

 

 

 

 

3

 

 

1

15

124

= 0,992.

P{1 :::;; X :::;; 5} = P{1 < X < 5} = f x4 dx = -3x3

1

= 125

 

 

 

 

1

 

 

 

 

 

 

 

350

6.9.6.HerrpephIBHaJI C. B. X HMeeT rrJIOTHOCTh pacrrpe)J;eJIeHHH BepOHTHO-

cTeii

34 , X ~ 1, f(x) = { x

0, x < 1.

HaiiTH ¢YHKIIHIO pacrrpe)J;eJIeHHH BepoHTHocTeii F(x); rrOCTpOHTh

rpa¢HKH f(x) H F(x).

o MCrrOJIh3yeM ¢OpMyJIy

F(x) = !x f(t) dt.

-<Xl

I1PH X E (-00,1) HMeeM:

x

F(x)= !O.dt=O.

-<Xl

TIPH X E [1, +00) rrpOMe:>KYTOK HHTerpHpOBaHHH pa36HBaeTcH Ha )J;Ba:

f(x)

F(x)

3 ----

26 1 ---------------------

 

27 ~

 

8"

o

1 2 3

x

o

1 2

x

 

 

Puc. 82

 

Puc. 83

TaKHM o6pa30M,

 

 

 

O,

X < 1,

F(x) =

{ l _ l

x~1.

 

X 3

 

'

rpa¢HKH ¢YHKIIHii f(x)

H F(x) rrpe)J;cTaBJIeHhI COOTBeTCTBeHHO Ha

puc. 82 H pHC. 83.

 

351

6.9.7. HeIIpepbIBHaH CJIY'IaiiHaH BeJIlI'IIIHa X paCIIpe,11,eJIeHa «IIO 3aKoHY IIpHMoyroJIbHOrO TpeyroJIbHIIKa» Ha IIHTepBaJIe (0,4); Ha pllC. 84

H306pIDKeHa IIJIOTHOCTb pacIIpe,11,eJIeHIIH 9TOii c. B. HaiiTII: a) 3Ha'leHlIe Yo;

6) aHaJIIITII'IeCKOe BbIpIDKeHlIe ,11,JIH IIJIOTHOCTII f(x) II <PYHKIIIIII

paCIIpe,11,eJIeHIIH F(x). llOCTPOIlTb rpa<PIIK F(x).

a a) TaK KaK IIJIOIII8,!I.b S <PlIrYPbI, OrpaHH'IeHHOii cBepxy KPIlBOii pacIIpe-

,11,eJIeHIIH (T. e. rpa<PIIKoM <PYHKIIIIII

f(x», a

CHlI3Y -

OCbIO Ox, paBHa 1, TO

1

1

 

S = S.6.AOB = 2" ·4· Yo = 1. OTCIO,11,a Yo = 2".

 

6) YpaBHeHlIe IIPHMOii AB Haii,11,eM KaK ypaBHeHlIe IIPHMOii, IIpOXO,11,HIIIeii

'Iepe3 TO'lKII A (O;~) II B(4;0»: 'J/= -kx+~. AHaJIIITII'IeCKOe BbIpIDKeHlIe

,l1,JlH IIJIOTHOCTII paCIIpe,11,eJIeHIIH c. B. X TaKOBO:

 

II

xE[0,4],

 

f(x)= { -8 x

+2"'

 

0,

 

x fi. [0,4].

 

f(x)

 

 

 

yo A

 

 

 

o

 

B

 

 

4

x

Puc. 84

TeIIepb Haii,11,eM <PYHKIIIIIO paCIIpe,11,eJIeHIIH F(x): x

eCJIII

x E (-00,0), TO F(x) = j Odt = 0;

 

- 00

eCJIII

x E [0,4], TO

o

x

 

 

 

 

 

+~.

F(x) = j

Odt + j(_lt + 1) dt = (-le + i) IX = _x2

 

8

2

16

2

0

16

2'

- 00

0

 

 

 

 

 

 

eCJIII x E (4,+00), TO

 

 

 

 

 

 

o

4

 

x

 

 

 

 

F(x)= jOdt+ j(-kt+~) dt+ jOdt=

 

 

 

 

- 00

0

 

4

 

 

 

 

= 0 + ( - ~~ + ~)I:+ 0 = -1 + 0 + 2 - 0 = 1.

352

TaKHM 06pa3oM,

 

O,

 

x < 0,

 

F(x) = {

X 2

X

°~ x ~ 4,

-16 + 2'

 

1,

 

x> 4.

fpa<pHK <PYHKlI.HH F(x) H306p8.)KeH Ha pHC. 85.

F(x)

 

 

 

 

 

 

 

 

-------------

 

:.:.-----

 

 

 

 

4

x

 

Puc. 85

 

 

6.9.8.,naHa nJIOTHOCTb pacnpe,11,eJIeHHg c. B. X:

O,

npH x < 0,

f(x) = { b·x,

npH °~ x < 5,8,

0,

npH 5,8 ~ x.

Onpe,11,eJIHTb nOCTOgHHYIO b, HaiiTH <PYHKlI.HIO pacnpe,11,eJIeHHg F(x)

H nOCTpOHTb ee rpa¢HK, BbI'IHCJIHTbBepOgTHOCTb Toro, "ITO C. B.

X npHMeT 3Ha"leHHe, Y,11,OBJIeTBOpgIOm;ee YCJIOBHIO:

a) X < 3,3;

6) 3,3 < X < 7,8.

6.9.9.llJIOTHOCTb BepOgTHOCTH c. B. X HMeeT BH,11,

f(x) = eX :e-x ' x E III

HaiiTH 3Ha"leHHe napaMeTpa a, <PYHKIJ.HIO pacnpe,11,eJIeH~ F(x).

6.9.10.CJIY"IaiiHM BeJIH"IHHa X HMeeT nJIOTHOCTb pacnpe,11,eJIeHHg

f(x) = {v'4~x 2 '

Ixl < 2,

0,

Ixl ~ 2.

HaiiTH:

a) 3Ha"leHHe napaMeTpa C;

6) <PYHKlI.HIO pacnpe,11,eJIeHHg F(x);

0)P{l < X < 5}.

6.9.11.3a,I1;aHa nJIOTHOCTb pacnpe,11,eJIeHHg H. c. B. X:

o,

x ~ 1,

f(x) = { 2x -

2, 1 < x ~ 2,

0,

2 < x.

12 CooPHH. _qno ....ew.A NBTCNlTH... 2 KypC

353

qTO BepmlTHee: nona,.u,rume CJIY'IaiiHOii Beml'IllHbI B IIHTepBaJI

(1,6; 1,8) IIJIII B (1,9; 2,6)?

6.9.12. 3a,.u,aHa nJIOTHOCTb pacnpe,II.eJIeHIIH H. c. B. X:

a,

x< -A,

f(x) = { -x,

-A::::; x <0,

2x,

o::::;x < A,

0,

A::::;x.

HaiiTII A, F(x), P{ -2 < X

< I}.

6.9.13. rpa<PIIK nJIOTHOCTII pacnpe,II.eJIeHIIH H. c. B. X IIMeeT BII,II., 1I306pa- :>KeHHblii Ha pllC. 86. 3anllcaTb aHaJIlITlI'IeCKOe Bblpa:>KeHlIe ,II.JIH nJIOTHOCTII pacnpe,II.eJIeHIIH f (x) .

F(x)

f(x)

1

-----------------------

r--------

 

 

I

 

 

:;:

I

 

0,5

I

 

 

x

o

 

x

Puc. 86

 

Puc. 87

 

 

F(x) = {3X ,

npll x ::::; 0,

 

1,

npll x > 0.

 

HaiiTII:

 

 

a) nJIOTHOCTb f(x);

 

 

6) BepOHTHOCTb Toro, 'ITOC. B. X B pe3YJIbTaTe onbITa npllMeT 3Ha-

 

'IeHlIeB IIHTepBaJIe (-1, 1).

 

6.9.15.

Ha pllC. 87 3a,.u,aH rpa<pIIK <PYHKIJ;1I11 pacnpe,II.eJIeHIIH c. B. X. HaiiTII

 

aHaJIlITlI'IeCKOeBblpa:>KeHlIe ,II.JIH:

 

a) F(x);

6) f(x).

 

IIOCTPOIlTb rpa<pIIK nJIOTHOCTII pacnpe,II.eJIeHIIH c. B. X.

6.9.16.

cDYHKIJ;IIH pacnpe,II.eJIeHIIH H. c. B. X 3a,.u,aHa Bblpa:>KeHlIeM

a,

F(x)= {a.sin(x+~)+b,

1,

354

 

Ha:lhH:

6) rrJIOTHOCTb f{x);

 

a) K09<P<lmIJ;HeHTbI a, b;

 

B)P{O~X<~}.

 

 

IIOCTPOHTb rpa¢HK <PYHKIJ;HH f{x).

6.9.17.

3a,n;aHa <PYHKIJ;Hg

 

 

O,

x ~ 0,

 

F{x)= { a·x2 ,

O<x~l,

 

1,

1 < x.

 

Orrpe,n;eJIHTb:

 

 

a) rrpH KaKOM 3Ha'leHHHa <PYHKIJ;Hg F{x) 6y,n;eT <PYHKIJ;He:li pac-

 

rrpe,n;eJIeHHg HeKoTopo:li c. B. X;

 

6) rrJIOTHOCTb BepOgTHOCTH c. B. X;

 

B) BepOgTHOCTb C06bITHg D = {- ~ ~ x ~ ~}.

6.9.1S.

cDYHKIJ;Hg pacrrpe,n;eJIeHHg C. B. X HMeeT BH,n; F{x) = a +arctg~,

 

x E lR. Ha:liTH:

 

 

a) 3Ha'leHHerrapaMeTpOB a H b;

 

6) rrJIOTHOCTb BepOgTHOCTH.

 

6.9.19.

cDYHKIJ;Hg pacrrpe,n;eJIeHHg H. c. B. X - BpeMeHH 6e30TKa3Ho:li pa6o-

 

 

x

 

TbI HeKoToporo rrpH60pa - paBHa F{x) = 1- e- T , x ~ 0. Ha:liTH

 

P {X > T}, T. e. BepOgTHOCTb 6e30TKa3Ho:li pa60TbI rrpH60pa 3a

 

BpeMg, 60JIblIIee T.

 

6.9.20.

)J;aHa <PYHKIJ;Hg

 

 

f{X)={A.x.e- x , x~O,

 

0,

x < 0.

 

IIPH KaKOM 3Ha'leHHHrrapaMeTpa A 9Ta <PYHKIJ;Hg gBJIgeTCg rrJIOT-

 

HOCTbIO pacrrpe,n;eJIeHHg HeKoTopo:li H. c. B. X? Ha:liTH F{x).

6.9.21. 3a,n;aHa rrJIOTHOCTb BepOgTHOCTH CJIY'Ia:liHo:liBeJIH'IHHbIX:

 

O,

x < -4,

 

f{x) = { -Ax,

-4 ~ x < 0,

 

Ay'x,

°~ x < 4,

 

0,

4 ~ x.

 

Ha:liTH A, F{x), P{ -1 < X < 5}.

6.9.22.

IIJIOTHOCTb BepOgTHOCTH H. c. B. X HMeeT BH,n;

 

0,

x< -A,

 

f{x) = ;~'

-A ~ x < 0,

 

12'

°~ x < 2A,

 

0,

2A ~x.

Ha:liTH A, F{x), P{ -0,5 < X < 2}.

355

KOHTponbHble BOnpOCbI M 60nee CnO)l(Hble 3aACIHMH

6.9.23. 3a,rJ;aHa HeKOTOpaJI <PYHKIJ;IUI

 

a,

x ~ -1,

F(x)= { i,(X+l)3,

-1 < x ~ 1,

1,

1 < x.

HBJIHeTCH JIH OHa <PYHKIJ;Heii pacrrpe,11,eJIeHHH HeKOTopoii CJIyqaiiHoii BeJIHqHHbI X? qeMY paBHa BepOHTHOCTb C06bITHH

A={O~X<I}?

6.9.24.

3HaqeHHH c. B. X HaxO,11,HTCH B

rrpOMe:>KYTKe

(OJ i). MO:>KeT JIH

 

<PYHKIJ;HH pacrrpe,11,eJIeHHH F(x) paBHHTbCH Ha 3TOM yqacTKe:

 

a) sinx;

6) X 2 j

 

 

B) 1,lj

r) COSXj

 

 

.n.) 2:?

 

 

6.9.25.

HerrpephIBHaJI c. B. X 3a,rJ;aHa <PYHKIJ;Heii pacrrpe,11,eJIeHHH

 

O'

x < -i,

 

 

F(x)= { a.sin(x-i)+b, _i~x~3;,

 

C,

371"

 

 

4" <x.

 

 

a) 3HaqeHHH a, b, Cj

 

 

 

6) rrJIOTHOCTb ! (x) pacrrpe,11,eJIeHHH c. B. X. ITOCTPOHTb rpa¢HKH

 

<PYHKIJ;Hii F(x) H !(x).

 

 

6.9.26.

cDYHKIJ;HH pacrrpe,11,eJIeHHH H. c. B. X, paBHaJI

 

 

a,

x ~ 1,

 

 

F(x) = {ax2 + bx + c,

1 < x ~ 2,

 

 

1,

2 < X.

 

 

cDYHKIJ;HH F(x) = ax2 + bx + C rrpH x = 2 HMeeT MaKCHMYM. HaiiTH:

 

a) rrapaMeTpbI a, b, Cj

 

= {I ~ X < 3},

 

6) BepOHTHOCTH C06bITHii A = {X > 3}, B

E = {X E ( - lj 1,5)}.

6.9.27.HerrpepbIBHaJI c. B. X pacrrpe,11,eJIeHa rro 3aKOHY JIanJIaca:

!(x) = e->"Izl, r,11,e A > 0.

HaiiTH K03<P<PHIJ;HeHT A H <PYHKIJ;HIO pacrrpe,11,eJIeHHH F(x). IToCTPOHTb rpa¢HKH !(x) H F(x).

6.9.28. HerrpepbIBHaJI c. B. X 3a,rJ;aHa <PYHKIJ;Heii pacrrpe,11,eJIeHHH

O'

 

x ~ y'3,

 

F(x) = { x6 -

X4 - 18

. '3<

~ 2

,

 

30

,v.,

x"

1,

 

2 < X.

 

 

HaiiTH P{I,8 < X < 2,8}, !(x)j rrocTpoHTb rpa¢HKH F(x) H !(x).

356

xapaICmepucmuICu nOArotCeH'U.fI
fx(x).

6.9.29. CJIY"IaftHruI Beml"lHHa X nO,!l;"IHHHeTCH 3aKOHY raycca:

f(x) =

(:I: +2)2

1 . e -- l - S -

 

v'21T

HaftTH ¢YHKIJ;HIO pacnpe,!l;eJIeHHH F(x), nOCTpOHTb rpa¢HKH ¢YHK-

IJ;Hft f(x) H F(x).

6.9.30. IIPH KaKOM 3Ha"leHHH napaMeTpa A ¢YHKIJ;HH

{~ Ixl ~ 1, f(x) = . (1 - Ix!), Ixl < 1

HBJIHeTCH nJIOTHOCTbIO pacnpe,!l;eJIeHHH HeKoTopoft H. c. B. X? IIo-

CTPOHTb rpa¢HK HaftTH ¢YHKIJ;HIO pacnpe,!l;eJIeHHH 9TOft

c.B. HaftTH

§10. l.IVlC110BbIE XAPAKTEPVlCTVlKVI C11Yl.IAtiHbIX BE11 Vll.I VI H

TIPH peIlIeHHH MHorHX 3a,n;a'lTeopHH BepOlITHOCTH BOBce He061I3aTeJIbHO 3HaTb 3aKOH pacnpe,1l;eJIeHHlI ,1I;aHHOit CJIY'IaitHOitBeJIH'IHHbI, nOJIHOCTbIO ee OnHCbIBaIOru;eil:. 3a'lacTYIO,1I;OCTaTO'lHOHMeTb no,1l; PYKOit JIHilib HeCKOJIbKO "'UCA061>tX xapaICmepucmuIC aToit CJIY'IaitHoitBeJIH'IHHbI,T. e. '1HCJIOBbIXnapaMeTpOB, xapaKTepH3YIOru;HX HaH60JIee BalKHbIe '1epTbIee 3aKOHa pacnpe,1l;eJIeHHlI. BalKHeitIlIHMH Cpe,1l;H HHX lIBJIlIIOTClI (MaTeMaTH'IeCKOeOlKH,1I;aHHe, Me,1l;H- aHa H T. ,11;.) H xapaICmepucmuICu paCCeslH'U.fI (,1I;HCnepCHlI, Cpe,1l;HeKBa,n;paTH'IeCKOeOTKJIOHeHHe H ,1I;p.).

~MameMamu",eCICuM rotCuiJaHueM (HJIH Cpe,1l;HHM 3Ha'leHHeM)M(X) (HJIH MX)

AHCKpeTHoit CJIY'IaitHoitBeJIH'IHHbI X Ha3bIBaeTClI CYMMa npOH3Be,1l;eHHit Bcex ee B03MOlKHbIX 3Ha'leHHitXi Ha HX COOTBeTCTBYIOIIIHe BepOlITHOCTH:

M(X) = L XiP.·

ECJIH ,11;. C. B. X npHHHMaeT KOHe'lHOe'1HCJIO3Ha'leHHitXl, X2, ••• , X", TO ee MaTeMaTH'IeCKOeOlKH,1I;aHHe HaxO,1l;HTClI no <popMYJIe

"

M(X) = L XiPi. i=l

ECJIH lKe ,11;. c. B. X npHHHMaeT C'IeTHOe'1HCJIO3Ha'leHHit,TO

00

M(X) =L :riPi;

i=l

npH aTOM M&TeMaTH'IeCKOeOlKH,1I;aHHe CYIIIecTByeT, eCJIH plI,1I; B npasoit '1acTHaToit <P0PMYJIbI a6COJIIOTHO CXO,1l;HTClI.

357

MaTeMaTll'leCKHMOlKH)l;aHHeM HenpepbIBHolt CJIY'IaltHoltBeJIH'IHHbIX C ITJIOT-

HOCTbIO BepOlITHOCTH I(x) HaxO)l;HTCli no <popMYJIe

M(X) = !00I(x) dx.

- 00

TIPH 9TOM MaTeMaTH'IeCKOeOlKH)l;aHHe cym;ecTByeT, eCJIH HHTerpaJI B npaBolt '1aCTH

<P0PMYJIbI a6COJIIOTHO CXO)l;HTClI (9TO 3Ha'lHT,'ITOCXO)l;HTCli HHTerpaJI !00 Ixl/(x) dx).

- 00

CBOMCTBa MaTeMan,...eCKoro O)l(MA'lHM5I

1.M(G) = G, r)l;e G = constj

2.M(GX) = M(X)j

3.M(X ± Y) = M(X) ± M(Y) (npaBHJIO CJIOlKeHHlI MaTeMaTH'IeCKHXOlKH)l;a-

HHlt)j

4. M(X . Y) = M(X) . M(Y), eCJIH X H Y - He3aBHCHMble CJIY'IaltHbleBeJIH-

'1HHbI(npaBHJIO YMHolKeHHlI MaTeMaTH'IeCKHXOlKH)l;aHHlt).

0603Ha'lHMMaTeMaTH'IeCKOeOlKH)l;aHHe c. B. X '1epe3a.

~ ,l(ucnepcueti (paccelIHHeM) CJIY'IaltHoltBeJIH'IHHbIX Ha3b1BaeTClI MaTeMaTH'IeCKoe OlKH)l;aHHe KBa)l;paTa OTKJIOHeHHll c. B. OT ee MaTeMaTH'IeCKOrOOlKH)l;aHHll a:

D(X) = M(X - a)2.

Cpa3Y H3 onpe)l;eJIeHHll BblTeKaeT '1acTOHCnOJIb3yeMaH <p0pMYJIa

ECJIH X -

)l;HCKpeTHalI CJIY'IaltHaHBeJIH'IHHa,TO ee )l;HCnepCHlI BbI'IHCJIlIeTClI

no <popMYJIe

 

 

 

 

 

n

 

 

n

D(X) = ~)Xi - a)2 . Pi,

T. e.

D(X) = L x~ . Pi - a2

 

i=l

 

 

i=l

B CJIY'IaeKOHe'lHOrO'1HCJIa3Ha'leHHlt,npHHHMaeMbIX C. B. X, H nc;> <p0pMYJIe

 

 

 

00

 

 

 

D(X) = L(Xi - a)2pi

 

 

 

i=l

 

(T. e. D(X) =

00

 

 

 

~ X~Pi -

a2 ) B CJIY'IaeC'IeTHOrO'1HCJIa3Ha'leHlIlt.

 

i=l

 

 

 

ECJIH X -

HenpepblBHalI CJIY'IaltHaHBeJIH'IHHaC nJIOTHOCTbIO I(x), TO

 

00

 

 

00

D(X) = !(x -

a)2 . I(x) dx,

HJIH

D(X) = ! x 2 I(x) dx - a2

 

- 00

 

 

- 00

358

CBoiiiCTBa AMCnepCMM

1.D(C) = 0, r,n;e C = constj

2.D(CX) = C2 . D(X)j

3. D(X ± Y) = D(X) + D(Y), eCJIH X H Y - He3aBHCHMble CJIY'IaitHbleBeJIH-

qHHbI (npaBHJIO CJIOlKeHHX ,n;HcnepcHit)j

4.D(X + C) = D(X).

~Cpea'HUM 7I:6aapamU"I.eC7I:UM om1CJlO'He'HUeM CJIY'IaitHoitBeJIH'IHHbIX Ha3bIBaeT-

Cfl '1HCJIOu(X), onpe,n;eJIXeMOe paBeHCTBOM u(X) = ..jD(X).

$

BeJIH'IHHau(X) HeOTpHn;aTeJIbHa H HMeeT TY lKe pa3MepHOCTb, 'ITOH C. B. X.

~ Ha"l.aJl'b'H'btM MOMe'HmOM nopx,n;Ka k (k = 0,1,2, ... ) CJIY'IaitHoitBeJIHqHHbI X Ha3bIBaeTCfl '1HCJIOOk, onpe,n;eJIXeMOe no <popMYJIe

eCJIH X - ,n;. C. B., H

00

Ok =

! xk. f(x)dx,

eCJIH X - H . C. B.

- 00

 

~ Lfe'HmpaJl'b'H'btM MOMe'HmOM nopJ/,a7l:a k C. B. X Ha3bIBaeTCfl '1HCJIOI-'k, onpe,n;e-

JIXeMOe no <popMYJIe

eCJIH X - ,n;. C. B., H

 

 

 

 

00

 

 

 

 

 

I-'k=

!(x-a)k·f(x)dx,

 

 

 

 

 

- 00

 

 

eCJIH X - H . C. B.

 

 

 

 

 

~

K03rjjifJUv,ue'Hm

aCUMMempuu

(<<c7I:owe'H'Hocmu»), HJIH, KOpO'le, aCHMMeTpHX

c. B. X eCTb BeJIH'IHHa

A=~.

 

 

 

 

 

 

 

 

 

 

 

 

u 3 (X)

 

 

~

K03rjjrjjuv,ue'Hm

371:cv,ecca (<<ocmpo6epWU'H'Hocmu»), HJIH,

nporn;e,

9KCn;ecc

C. B. X, eCTb BeJIH'IHHa

 

 

 

 

 

 

E=~-3.

 

 

 

 

 

 

u 4 (X)

 

 

~ Moaa a. C. 6. X

-

eCTb ee HaH60JIee BepOXTHoe 3Ha'leHHeMo(X). Moaa 'H. c. 6.

X

C nJIOTHOCTbIO f(x)

eCTb TO ee 3Ha'leHHeMo(X), npH KOTOPOM <PYHKn;Hx f(x)

)J,OCTHraeT MaKCHMYMa.

 

 

$

~ Meaua'Ha CJIY'IaitHoitBeJIH'IHHbI X (o603Ha'leHHe Me(X» -

eCTb

TaKoe ee

3Ha'leHHex p, ,n;JIX KOToporo o,n;HHaKOBO BepoflTHo, OKalKeTCfl JIH c. B. X MeHbIIIe xp

HJIH 60JIbIIIe x p , T. e.

1

PiX < x p } = PiX > Xp} = "2.

359

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