题目

More than 20 years ago, a skeleton called Little Foot turned up in a South African cave. The nearly complete skeleton was a member of the human family. Now researchers have freed most of the skeleton from its stony shell and analyzed the fossils (化石) and they say 3.67-million-years-old Little Foot belonged to a unique species.Researcher Ronald Clarke and his colleagues think Little Foot belonged to A. Prometheus (普罗米修斯南猿). Clarke works at the university of the Witwatersrand in Johannesburg South Africa. He studies fossilized humans and our relatives. Their foundings, publishe已知中心在原点O，焦点在x轴上的椭圆上的点到焦点距离的最大值为，最小值为．（1）求椭圆的方程（2）设过点的直线l与椭圆交于A、B两点，若以AB为直径的圆与y轴相切，求直线l的方程．