uses crt;
type mt=array[1..5,1..5] of real;
mang=array[1..5] of real;
function chuan1(b:mt;n:integer):real;
var i,j:integer;s:real;

begin
i:=1;
s:=0;
WHILE (i<=n) and (s<1) do
begin
s:=0;
FOR j:=1 to n do
s:=s+abs(b[i,j]);
i:=i+1;
end;

{if i>n THEN chuan1:=true
ELSE chuan1:=false;}
chuan1:=s;
end;
Var a,b:mt;f,g,x,y:mang;n,i,j,m,k,l,h:integer;
D,ss:real;kt,ktra,co:boolean;
Begin
clrscr;
textmode(co80);
repeat
write('Giai he bao nhieu phuong trinh:');
readln(n);
until (n>=2) and (n<=5);
writeln('Nhap ma tran cac he so:');
nhapmt(a,n);
writeln('Nhap cac he so tu do:');
FOR i:=1 to n do
begin
write('Nhap f[',i,']=');
readln(f[i]);
end;
writeln('Ma tran cac he so vua nhap la:');
xuatmt(a,n);
writeln('Ma tran cac he so tu do:');
FOR i:=1 to n do
writeln(f[i]:8:3);
D:=dtcn(a,n);
writeln('D=',d:0:4);
if D<>0 THEN
begin
FOR i:=1 to n do
FOR j:=1 to n do
if i=j THEN b[i,j]:=0
ELSE b[i,j]:=-a[i,j]/a[i,i];
FOR i:=1 to n do
g[i]:=f[i]/a[i,i];
writeln('Ma tran tuong duong B :');
xuatmt(b,n);
writeln('Ma tran cac he so G:');
FOR i:=1 to n do
writeln(g[i]:8:3);
kt:=false;
if chuan1(b,n)<1 THEN kt:=true
writeln('chuan 1 = ',chuan1(b,n):0:4);
if kt=true THEN
begin
write('Nhap sai so:');
readln(ss);
FOR i:=1 to n do
x[i]:=0;
ktra:=false;
WHILE ktra=false do
begin
FOR j:=1 to n do
begin
y[j]:=0;d:=0;
FOR k:=1 to n do
y[j]:=y[j]+b[j,k]*x[k];
y[j]:=y[j]+g[j];
if abs(y[j]-x[j])>ss THEN d:=d+1;
x[j]:=y[j];
end;
if d=0 THEN ktra:=true;
FOR i:=1 to n do
writeln('x',i,'=',x[i]:0:4);
readln;
end;
writeln('Nghiem cua he voi sai so ',ss:0:4,' la : ');
FOR i:=1 to n do
writeln('x',i,'=',x[i]:0:4);
end
ELSE writeln('Khong hoi tu');
end;
readln;
End.


!======================
Bài này down trên mạng đầy rẫy, ti tỉ phần mềm, việc gì phải vào đây đề nghị....
Pó tay chấm com