program progonka;
Uses Crt;
  const n=4;
  var a:array[1..n,1..n] of real;
      f,x,a1,b1:array[1..n] of real;
      i,j:integer;
        y,y1:real;
 begin
  ClrScr;
  for i:=1 to n do
    begin
      writeln ('введите коэффициенты в ',i,' строке');
      for j:=1 to n do
        readln (a[i,j]);
    end;
  writeln;
  writeln ('введите свободные члены');
  for i:=1 to n do
    readln (f[i]);
  ClrScr;
  a1[1]:=a[1,2]/a[1,1];b1[1]:=-f[1]/a[1,1];
  for i:=2 to n-1 do
   begin
       a1[i]:=a[i,i+1]/(a[i,i]-a[i,i-1]*a1[i-1]);
       b1[i]:=(a[i,i-1]*b1[i-1]-f[i])/(a[i,i]-a[i,i-1]*a1[i-1]);
   end;
   b1[n]:=(a[n,n-1]*b1[n-1]-f[n])/(a[n,n]-a[n,n-1]*a1[n-1]);
   x[n]:=b1[n];
   for i:=n-1 downto 1 do
    x[i]:=a1[i]*x[i+1]+b1[i];
    writeln ('Ответ:');
   for i:=1 to n do
     write (x[i]:2:2,' ');
   writeln;
   writeln('проверка');
   y:=5*x[1]-x[2]-2;
   writeln('y=',y:1:2);
   y1:=2*x[1]+4.6*x[2]-x[3]-3.3;
   writeln('y1=',y1:1:2);
   readln;
end.