function hypo(form) {
      a=eval(form.a.value);
      b=eval(form.b.value);
      c=eval(form.c.value.replace(",", "."));
      d=eval(form.d.value);
      x1=a-b;
      x2=(x1*c/12/100*Math.pow((1+c/12/100),12*d))/(Math.pow((1+c/12/100),12*d)-1);
      form.x1.value=x1;
      form.x2.value=Math.round(x2);
    }