They didn't have much money, so when it was timefor their summer holidays, Bill said, 'Let's take our holidays in a trailer (旅行车). It's cheaper ... 查看完整题目与答案 无论a取什么实数,方程x2+2y2-ax+ay-a-1=0表示的椭圆都和一条定直线相交,且截得的弦长为定值,则这...