
A = [ 1 -2 3 0;
      0 -2 3 1;
      0 0 -1 2;
      0 0 0 -2]

b = [3 3 -4 2]'

disp(' Standard - row') 

x = backsolv0(A, b) ;
x'

pause

disp(' Standard - row - version 2') 

x = backsolv(A, b) ;
x'

pause

disp(' Standard - column ')
 
x = backsolv_c(A, b) ;
x'

pause

disp(' Exact from matlab') 
x = A\b;
x'
