Pascal/Turbo Pascal - problema con la raíz

begin

  writeln ('operando1');

  read (A);

  writeln ('operando2');

  read (B);

  writeln ('operando3');

  read (C);

  D:=(sqrt(B*B-4*A*C));

  if D<0 then

     writeln ('error')

  else

    begin

         res1:=(-B+D)/(2*A);

         writeln (res1);

         res2:=(-B-D)/(2*A);

         writeln (res2);

         if res1=res2 then

            writeln ('una sola solución')

         else

             writeln ('dos soluciones');

    end;

     read (tonta);

end.

{Mira tu programa retocado}

uses

   crt;

var

   a, b, c : integer;

   d : real;

   res1, res2 : real;

begin

clrscr;

write('operando1 : ');

read(A);

write('operando2 : ');

read(B);

write('operando3 : ');

read(C);

D := sqrt(((B * B) - 4) * (A * C));

if D<0 then

writeln('error')

else

begin

res1 := (-B+D)/(2*A);

writeln('   ',res1:0:3);

res2 := (- B - D) / (2 * A);

writeln('   ',res2:0:3);

if res1 = res2 then

writeln('   una sola solución')

else

writeln('   dos soluciones');

end;

writeln('  Pulse Una Tecla');

readkey;

end.