7.“珍爱生命,拒绝毒品”,学校举行的2017年禁毒知识竞赛共有60道题,曾浩同学答对了x道题,答错了y道题(不答视为答错),且答对题数比答错题数的7倍还多4道,那么下面列出的方程组中正确的是( )
| A. | $\left\{\begin{array}{l}{x+y=60}\\{x-7y=4}\end{array}\right.$ | B. | $\left\{\begin{array}{l}{x+y=60}\\{y-7x=4}\end{array}\right.$ | C. | $\left\{\begin{array}{l}{x=60-y}\\{x=7y-4}\end{array}\right.$ | D. | $\left\{\begin{array}{l}{y=60-x}\\{y=7x-4}\end{array}\right.$ |
6.在射击训练中,小强哥哥射击了五次,成绩(单位:环)分别为:8,9,7,10,9,这五次成绩的众数和中位数分别是( )
| A. | 9,9 | B. | 7,9 | C. | 9,7 | D. | 8,9 |
3.2017的倒数是( )
| A. | $\frac{1}{2017}$ | B. | 2017 | C. | -2017 | D. | -$\frac{1}{2017}$ |
1.一个等腰三角形的两边长分别为$\sqrt{2}$、$\sqrt{10}$,则这个三角形的周长为( )
| A. | $\sqrt{10}$+2$\sqrt{2}$ | B. | $\sqrt{2}$+2$\sqrt{10}$ | C. | $\sqrt{2}$+4$\sqrt{5}$ | D. | $\sqrt{10}$+2$\sqrt{2}$或$\sqrt{2}$+2$\sqrt{10}$ |
20.下列各式计算中,正确的是( )
| A. | $\sqrt{(-4)(-9)}$=$\sqrt{-4}$×$\sqrt{-9}$=6 | B. | $\sqrt{{8}^{2}+{9}^{2}}$=8+9=17 | ||
| C. | $\sqrt{4{1}^{2}-4{0}^{2}}$=$\sqrt{81}$×$\sqrt{1}$=9 | D. | 3$\sqrt{\frac{2}{3}}$=$\sqrt{2}$ |
19.已知$\sqrt{x+2}$有意义,则x的取值范围是( )
0 297945 297953 297959 297963 297969 297971 297975 297981 297983 297989 297995 297999 298001 298005 298011 298013 298019 298023 298025 298029 298031 298035 298037 298039 298040 298041 298043 298044 298045 298047 298049 298053 298055 298059 298061 298065 298071 298073 298079 298083 298085 298089 298095 298101 298103 298109 298113 298115 298121 298125 298131 298139 366461
| A. | x≥-2 | B. | x≠-2 | C. | x>-2 | D. | x≥2 |