已知:抛物线 的顶点为 A ,与 x 轴的交点为 B , C (点 B 在点 C 的左侧). (1)直接写出抛物线对称轴方程; (2)若抛物线经过原点,且△ ABC 为直角三角形,求 a , b 的值; (3)若 D 为抛物线对称轴上一点,则以 A , B , C , D 为顶点的四边形能否为正方形?若能,请写出 a , b 满足的关系式;若不能,说明理由.
【简答题】A.They don't have to pay for the medical services. B.They needn't pay the entire medical bill at once. C.They must send the receipts to the insurance company promptly. D.They have to pay a much higher...