.
. ( .)
=
(-1)ti+tjai1j1*ai2j2*ai3j3**ainjn.
, .
det AT = det A
1) 2 , .
: . -> 2 -> -> .
2) 2 () , det = 0.
2 , , - 2 . , △=0. (△=-△, 2△=0, △=0)
3) 2 , = 0.
det = k det
, k , 2 . - 3 △ =0.
4) 1 , k- (αck1 + βdk1 + αck2+ βdk2) = α|ck1+ck2+ckn|+β|dk1+dk2+dkn|.
5) , .
6) , = 0.
7) - , = 0.
1 = (a11,a1n)
2 = (a21,a2n)
n = (an1,ann)
1 | |
Det A= | 2 |
n |
k
k = α1 1 + α2 2 ++ αk-1 k-1 + αk+1 k+1 ++ αn n
7 , . = (n-1) .
.
aik n-1 , , aik.
ik aik Aik = (-1)i+kMik.
. - .
det A = ak1Ak1+ak2Ak2++aknAkn =
1) : :
=
a11
1 , 1 1 .
, 1 .
2) :
= (-1)j
an1 an2 an3 an4 anm
akj ( j) 1 . (-1)j :
anj an1 an2 an3 anm
k , 1 , .. :
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anj an1 an2 an3 anm
(-1)k.
anj an1 an2 an3 anm
1 , .
det A = (-1)j+kakjMkj+0*Ak1++0*Ak2 **0*Akn
3) .
a11 | a12 | a1m | |
ak1 | ak2 | akm | |
an1 | an2 | anm |
=(-1)k+1ak1Mk1+(-1)k+2ak2Mk2++(-1)k+naknMkn
I ().
2. (, ()).
- , ..:
(*) k1j1+ k2j2++ knjn=0
:
:
j- | aj1 | aj2 | ajn | = j1j1+ j2j2++ jnjn (**) | |
k- | ak1 | ak2 | akn |
(*) jm j- -> jm , j- .
(**) j- k- . det = k1j1+ k2j2++ knjn
, . ...
3. . .
nm.
K- (k<m,k<n) , , - - .
, r=Rang , , r≠0, (r+1 ) =0.
.
k- , k+1 , :
k- k+1 , k+1 = 0.
3- M2: (, 2≠0)
11 | 12 | 13 | 14 |
21 | 22 | 23 | 24 |
31 | 32 | 33 | 34 |
41 | 42 | 43 | 44 |
11 | 12 | 13 | |
M3(1)= | 21 | 22 | 23 |
31 | 32 | 33 |
11 | 13 | 14 | |
M3(2)= | 21 | 23 | 24 |
31 | 33 | 34 |
11 | 12 | 13 | |
M3(3)= | 21 | 22 | 23 |
41 | 42 | 43 |
11 | 13 | 14 | |
M3(4)= | 21 | 23 | 24 |
41 | 43 | 44 |
4. . () . 0 .
r ( ) .
. ( ).
:
a11 | a12 | a1r | a1j | a1r+1 | a1n | ||
a21 | a22 | a2r | a2j | a2r+1 | a2n | ||
a31 | a32 | a3r | a3j | a3r+1 | a3n | ||
ar1 | ar2 | arr | arj | arr+1 | arn | ||
ak1 | ak2 | akr | akj | akr+1 | akn | ||
am1 | am2 | amr | mj | amr+1 | amn |
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|
k. . j. Mr+1, . K- , k- .
:
Mr+1=0=c1a1j+ c2a2j+ crarj+ Arakj |:Ar (Ar≠0)
Akj=-c1*a1j/Ar- c2*a2j/Ar+- cr*arj/Ar
akj k, ( ci/Ar j) ->
ak=-c1a1/Ar- c2a1/Ar -crar/Ar
:
, <n ( )
:
11 | 12 | 1n | |
21 | 22 | 2n | |
m1 | m2 | mn |
det A = 0
Rang A < n
1) : : det A = 0, : Rang A<n
det A = 0, . , < n. Rang A -> r<n
2) : : Rang A<n, : det A = 0
Rang A<n, , <n. , , , det A = 0 ( - ).
(), , .
11 | 12 | 1n | |
21 | 22 | 2n | |
m1 | m2 | mn |
( aij (j=1,2,3n))
1=(11, 12, 13,,1n);
2=(21, 22, 23,,2n);
m=(m1, m2, m3,,mn);
, , .. , 0, , .
1 1 + 2 2 + + m m , 1 = 2 = n = 0. .
, : ak= 1 1 + 2 2 + + k-1 k-1 + k+1 k+1 + n n
5. . .
1, 2, , n
aik
:
11 | 12 | 1n | |
21 | 22 | 2n | |
m1 | m2 | mn |
1) 1- .
2) .
*x1 + *x2 + + *xn =
3) . ( ). △2, - △2
△≠0, , , , :
△ , .
△i , △ .
△ = 0:
△i ≠ 0, (ᴓ) ( )
△i = 0, . .
1, 2, , n , , , , , .
6. . .
, Rang , , Rang Y , .. , A .
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11 | 12 | 1n | b1 | |
21 | 22 | 2n | b2 | |
m1 | m2 | mn | b3 |
Rang A = Rang
(*) a1x1 + a2x2 ++ anxn =b
1) : : , : Rang A = Rang
: , , , x1=c1, x2=c2, xn=cn, (*) . , b .
1x1 + 2x2 ++ nxn =
-> . , , Rang , .. Rang A = Rang
2) :
: Rang A = Rang
: (*) .
: A .. , . , . .. c1, c2, c3,,cn, 1c1+ 2c2++ ncn= . (*)
-> (*) x1=c1, x2=c2, xn=cn ...
.. 1,2,n .
.
. . / -- , , , , , , , . . . . , , , . , , , , ..
, , , , . , , , -
.
, .
.
, . , . ,
. . , , . , . . , . , , . , - , , - , , ( , ). . , . , , , -- .. . , , 1, -- . , . 1, -- , .. 15.4 : " , ? ." , , , , , , .
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.