9.抽查的甲、乙两班部分学生的视力,记录如下:
(1)求两组数据的平均数,众数,中位数.
(2)比较两组数据的特征,谈谈对“极端值”的认识.
| 甲班 | 0.1 | 0.9 | 1.0 | 1.1 | 1.1 | 1.3 | 1.5 |
| 乙班 | 0.8 | 0.9 | 1.0 | 1.1 | 1.1 | 1.3 | 1.5 |
(2)比较两组数据的特征,谈谈对“极端值”的认识.
7.下列方程组中是二元一次方程组的是( )
| A. | $\left\{\begin{array}{l}{x-y=3}\\{xy=1}\end{array}\right.$ | B. | $\left\{\begin{array}{l}{2x+y=5}\\{x=3y-2}\end{array}\right.$ | C. | $\left\{\begin{array}{l}{{x}^{2}-y=1}\\{y=2x}\end{array}\right.$ | D. | $\left\{\begin{array}{l}{\frac{1}{y}-\frac{1}{x}=2}\\{x+y=0}\end{array}\right.$ |
4.方程x2-$\frac{10}{x}$+1=-4x的正数根的取值范围是( )
| A. | 0<x<1 | B. | 1<x<2 | C. | 2<x<3 | D. | 3<x<4 |
1.下列式子没有意义的是( )
0 294166 294174 294180 294184 294190 294192 294196 294202 294204 294210 294216 294220 294222 294226 294232 294234 294240 294244 294246 294250 294252 294256 294258 294260 294261 294262 294264 294265 294266 294268 294270 294274 294276 294280 294282 294286 294292 294294 294300 294304 294306 294310 294316 294322 294324 294330 294334 294336 294342 294346 294352 294360 366461
| A. | $\sqrt{-(-2)}$ | B. | $\sqrt{0}$ | C. | $\sqrt{-2}$ | D. | $\sqrt{(-2)^{2}}$ |