Obliczanie wartości funkcji

program f1;
uses crt;
const napis='program oblicza f(x)=(x+y)/(x-y)';
var x,y:integer
 l,m:integer;
 f:real;
begin
  clrscr;
  writeln(napis);
  writeln('podaj x i y');
  read(x,y);
  writeln('x= ',x);writeln('y= ',y);
  l:=x-y;
  m:=x+y;
  f:=l/m;
  write('f= ',f:5:3);
  readkey
end.