1.抛物线y=-x2+6x-9的顶点为A,与y轴的交点为B,如果在抛物线上取点C,在x轴上取点D,使得四边形ABCD为平行四边形,那么点D的坐标是( )
| A. | (-6,0) | B. | (6,0) | C. | (-9,0) | D. | (9,0) |
20.与4-$\sqrt{6}$最接近的整数是( )
| A. | 0 | B. | 1 | C. | 2 | D. | 3 |
19.次数为3的单项式可以是( )
| A. | 3ab | B. | ab2 | C. | a3+b3 | D. | a3b |
18.已知,圆锥的高h=$2\sqrt{3}$cm,底面半径r=2cm,则圆锥的侧面积为( )cm2.
0 282721 282729 282735 282739 282745 282747 282751 282757 282759 282765 282771 282775 282777 282781 282787 282789 282795 282799 282801 282805 282807 282811 282813 282815 282816 282817 282819 282820 282821 282823 282825 282829 282831 282835 282837 282841 282847 282849 282855 282859 282861 282865 282871 282877 282879 282885 282889 282891 282897 282901 282907 282915 366461
| A. | 4$\sqrt{3}$π | B. | 8π | C. | 12π | D. | (4$\sqrt{3}$+4)π |