8.某同学对甲、乙、丙、丁四个市场五月份每天的白菜价格进行调查,计算后发现这四个市场的平均价格相同,方差分别为s甲2=10.1,s乙2=8.5,s丙2=6.5,s丁2=2.6,则五月份白菜价格最稳定的市场是( )
| A. | 甲 | B. | 乙 | C. | 丙 | D. | 丁 |
7.已知关于x的一元二次方程mx2+2mx+2-m=0有两个相等的实数根,则m的值是( )
| A. | -2 | B. | 1 | C. | 1或0 | D. | 1或-2 |
6.要使$\frac{\sqrt{x+2}}{x}$有意义,则x的取值范围是( )
0 284630 284638 284644 284648 284654 284656 284660 284666 284668 284674 284680 284684 284686 284690 284696 284698 284704 284708 284710 284714 284716 284720 284722 284724 284725 284726 284728 284729 284730 284732 284734 284738 284740 284744 284746 284750 284756 284758 284764 284768 284770 284774 284780 284786 284788 284794 284798 284800 284806 284810 284816 284824 366461
| A. | x>-2 | B. | x≠0 | C. | x≥-2且x≠0 | D. | x>-2且x≠0 |