שינויים

[http://math-wiki.com/index.php?title=88-280_%D7%AA%D7%A9%D7%A2%D7%95_%D7%A1%D7%9E%D7%A1%D7%98%D7%A8_%D7%90/%D7%AA%D7%A8%D7%92%D7%99%D7%9C%D7%99%D7%9D dfexercise1]