5.
如图,△ABC以O为旋转中心,旋转180°后得到△A′B′C′,ED是△ABC的中位线,经旋转后为线段 E′D′.已知BC=4,则E′D′等于( )
| A. | 4 | B. | 3 | C. | $\frac{5}{2}$ | D. | 2 |
1.若x2-kx+9是一个完全平方式,则k的值为( )
0 284766 284774 284780 284784 284790 284792 284796 284802 284804 284810 284816 284820 284822 284826 284832 284834 284840 284844 284846 284850 284852 284856 284858 284860 284861 284862 284864 284865 284866 284868 284870 284874 284876 284880 284882 284886 284892 284894 284900 284904 284906 284910 284916 284922 284924 284930 284934 284936 284942 284946 284952 284960 366461
| A. | -3 | B. | -6 | C. | ±3 | D. | ±6 |