18的因数____;8的倍数(100以内)____
小王想给国外的杂志社发篇文章,他选择最便捷的方式是( )
— I'm sorry I ____ (leave) my exercise book at home.
— Don't forget to bring it to school tomorrow, please.
已知动圆C过点(1,0),且于直线x=﹣1相切.
(1)求圆心C的轨迹M的方程;
(2)A,B是M上的动点,O是坐标原点,且OA→·OB→,求证:直线AB过定点,并求出该点坐标.