составить программу решения системы линейных алгебраических уравнений

uses crt;
const s=4;
type a=array[1..s,1..s] of real;
var
a1,a2:a;
x,b:array[1..s] of real;
i,j,m,n:byte;
dx,dxx:real;
function det(a2:a):real;
var
y,z:a;
i,j,k:byte;
sum,d:real;
begin
for i:=1 to s do begin
y[i,1]:=a2[i,1];
z[i,i]:=1;
end;
for j:=1 to s do z[1,j]:=a2[1,j]/y[1,1];
for i:=2 to s do
for j:=2 to s do begin
if (j>=2) and (i>=j) then begin
sum:=0;
for k:=1 to j-1 do sum:=sum+y[i,k]*z[k,j];
y[i,j]:=a2[i,j]-sum;
end;
if (i>=2) and (j>=i) then begin
sum:=0;
for k:=1 to i-1 do sum:=sum+y[i,k]*z[k,j];
if y[i,i]<>0 then z[i,j]:=(a2[i,j]-sum)/y[i,i];
end;
end;
d:=1;
for i:=1 to s do d:=d*y[i,i];
det:=d;
end;
begin
clrscr;
writeln('a1');
for i:=1 to s do begin
write('-->');for j:=1 to s-1 do read(a1[i,j]);
readln(a1[i,s]); end;
writeln('b');
for i:=1 to s do read(b[i]);
for n:=1 to s do
for m:=1 to s do a2[n,m]:=a1[n,m];
dx:=det(a2);
for j:=1 to s do begin
for n:=1 to s do
for m:=1 to s do a2[n,m]:=a1[n,m];
for i:=1 to s do a2[i,j]:=b[i];
dxx:=det(a2);
x[j]:=dxx/dx;
write('x',j,'=',x[j]:8:3);
end;
readkey;
end.

Procedure Kramera(var
 k2,k3,k4,k6,k7,k8,k10,k11,k12,k14,k15,k16:real);
var
x,y,z,D,Dx,Dy,Dz:real;begin 
D=(k2*k7*k12)+(k4*k6*k11)+(k3*k8*k10)-(k4*k7*k10)-(k2*k8*k11)-(k3*k6*k12);
 if D<>0 then
  begin
   Dx:=(k14*k7*k12)+(k8*k10*k15)+(k6*k11*k16)-(k7*k10*k16)-(k15*k6*k12)-(k14*k8*k11);
   Dy:=(k2*k15*k12)+(k3*k16*k10)+(k4*k14*k11)-(k4*k15*k10)-(k3*k14*k12)-(k2*k16*k11);
   Dz:=(k2*k7*k16)+(k3*k8*k14)+(k4*k6*k15)-(k4*k7*k14)-(k8*k15*k2)-(k3*k6*k16);
   x:=Dx/D;
   y:=Dy/D;
   z:=Dz/D;
writeln('x=',x:4:2);
writeln('y=',y:4:2);
writeln('z=',z:4:2);
  end
  else
Showmessage('net resheniy');
end;