procedure CHOBSB(A:MATRX2; N:integer; D:array of real;var B:array of real);
var
    I,J:integer;  SUM:real;
begin
    For I:=1 To N do
    begin
        Sum:=B[I];
        For J:=1 To I - 1 do
            Sum:=Sum - A[I, J] * B[J];
        B[I]:=Sum;
    end;
    For I:=N DownTo 1 do
    begin
        If D[I] = 0 Then
        begin
            ShowMessage('Singular Matrix');
            Exit;
        end
        Else
            Sum:=B[I] / D[I];
        For J:=I + 1 To N do
            Sum:=Sum - A[J, I] * B[J];
        B[I]:=Sum;
    end;
end;