- , ..
(i = 1, 2,..., n)
n n 1, 2,n .
a11x1+a12x2++a1nxn=b1
a21x1+a22x2++a2nxn=b2 (1)
.
an1x1+an2x2++annxn=bn
(1) n n .. n- . :
a11a12a1n
D= a21a22a2n
.
an1an2ann
.j- .. xj, Aj;, . Dj(B) , D Aj B.
a11a12b1a1n
Dj()= a21a22b2a2n
.
an1an2bnann
.. : n 0, . , :
xj=Dj()/D (j=1,2,,n) (2)
: , D<>0, (1) .
(1):
a11a12a1n b1
a21a22a2n b1
an1an2ann bn
n- . :
a11 a11 a1n b1
I1= a21, I2= a22, In= a2n, b= b2
a..
an1 an2 ann bn
D, (I1, I2, In) 0. .
, (1) :
X1I1+x2I2++xnIn=b
, x1, x2,xn - b . , , . (1) .
, (1) (2) D<>0
, 1, 2, ,n (1) j- D Xj. D Xj. :
11 12 j1j 1n
a12 22 j2j 2n
Dxj = ..
n1 n2 xjanj nn
j- , : 1, 2, . ., n.
, , j , j .
1 j : 111+122++1jj++1nn
1 (1). .. 1, 2, , n (1), b1. 1 j , b1, b2, (n ) bn
|
|
Dxj :
11 12 b1 a1n
a21 a22 b2 2n = Dj(b)
n1 an2 bn nn
, Dxj=Dj(b)
, Xj=D(b)/D
xj 1, 2, n. (1) (2).
:
1 2 33 = 8
{ 21 + 2 3 = - 1
-21 + 2 = - 3
:
1 -1 3
D = 2 1 -1 = -2+6+6+1=11 <> 0
-2 1 0
. . D <> 0, . :
8 -1 3
D1 = -1 1 -1 = -3-3+9+8=11
-3 1 0
1 8 3
D2 = 2 -1 -1 = 16-18-6-3=-11
-2 -3 0
1 -1 8
D3 = 2 1 -1 = -3-2+16+16+1-6=22
-2 1 -3
X1 = D1/D= 1; X2 = D2/D = -1; X3 = D3/D =2
: (1; -1; 2)