-->[L,U]=LU1(A)   
 A  =
 
!   4.    5.    3. !
!   3.    4.    2. !
!   2.    3.  - 1. !
pivot=4.000000
etape 1
 A  =
 
!   4.    1.25    0.75 !
!   3.    0.25  - 0.25 !
!   2.    0.5   - 2.5  !
pivot=0.250000
etape 2
 A  =
 
!   4.    1.25    0.75 !
!   3.    0.25  - 1.   !
!   2.    0.5   - 2.   !
pivot=-2.000000
etape 3
 A  =
 
!   4.    1.25    0.75 !
!   3.    0.25  - 1.   !
!   2.    0.5   - 2.   !
 U  =
 
!   1.    1.25    0.75 !
!   0.    1.    - 1.   !
!   0.    0.      1.   !
 L  =
 
!   4.    0.      0. !
!   3.    0.25    0. !
!   2.    0.5   - 2. !
 
-->L*U         
 ans  =
 
!   4.    5.    3. !
!   3.    4.    2. !
!   2.    3.  - 1. !
 
-->L*U-A
 ans  =
 
!   0.    0.    0. !
!   0.    0.    0. !
!   0.    0.    0. !