题目

通过直线y=x和圆x2+y2+6x=0的交点,且对称轴是坐标轴的抛物线方程是____________. 答案：y2=-3x或x2=-3y解析:联立解得交点为(0,0),(-3,-3).所以抛物线方程为y2=-2px(p＞0)或x2=-2py(p＞0),将点(-3,-3)分别代入即可求得. The number of people invited ________ fifty, but a number of them ________ absent for different reasons． [　　] A．were; was B．was; was C．was; were D．were; were