4.二元一次方程组$\left\{\begin{array}{l}{x+y=5}\\{2x-y=4}\end{array}\right.$的解为( )
| A. | $\left\{\begin{array}{l}{x=1}\\{y=4}\end{array}\right.$ | B. | $\left\{\begin{array}{l}{x=2}\\{y=3}\end{array}\right.$ | C. | $\left\{\begin{array}{l}{x=3}\\{y=2}\end{array}\right.$ | D. | $\left\{\begin{array}{l}{x=4}\\{y=1}\end{array}\right.$ |
3.下列计算结果正确的是( )
| A. | a8÷a4=a2 | B. | a2•a3=a6 | C. | (a3)2=a6 | D. | (-2a2)3=8a6 |
2.一组数据8,3,8,6,7,8,7的众数和中位数分别是( )
0 284549 284557 284563 284567 284573 284575 284579 284585 284587 284593 284599 284603 284605 284609 284615 284617 284623 284627 284629 284633 284635 284639 284641 284643 284644 284645 284647 284648 284649 284651 284653 284657 284659 284663 284665 284669 284675 284677 284683 284687 284689 284693 284699 284705 284707 284713 284717 284719 284725 284729 284735 284743 366461
| A. | 8,6 | B. | 7,6 | C. | 7,8 | D. | 8,7 |