8.在社会实践活动中,某同学对甲、乙、丙、丁四个城市一至五月份的白菜价格进行调查,四个城市五个月白菜价格的平均值均为3.50元,方差分别为S甲2=18.3,S乙2=17.4,S丙2=20.1,S丁2=12.5,则一至五月份白菜价格最稳定的城市是( )
| A. | 甲城市 | B. | 乙城市 | C. | 丙城市 | D. | 丁城市 |
4.下列运算正确的是( )
| A. | (3$\sqrt{2}$)2=6 | B. | 3$\sqrt{{2}^{2}}$=6 | C. | (-2$\sqrt{3}$)2=6 | D. | (-3$\sqrt{2}$)2=6 |
3.$\sqrt{2}$的相反数是( )
0 284638 284646 284652 284656 284662 284664 284668 284674 284676 284682 284688 284692 284694 284698 284704 284706 284712 284716 284718 284722 284724 284728 284730 284732 284733 284734 284736 284737 284738 284740 284742 284746 284748 284752 284754 284758 284764 284766 284772 284776 284778 284782 284788 284794 284796 284802 284806 284808 284814 284818 284824 284832 366461
| A. | $\sqrt{2}$ | B. | -$\sqrt{2}$ | C. | 2 | D. | -2 |