I didn't do very well in this exam. Unluckily, he did it .
A:worse
B:badly
C:better
D:worst
已知:A=ax2+x﹣1,B=3x2﹣2x+1(a为常数)
①若A与B的和中不含x2项,则a等于?
②在①的基础上化简:B﹣2A.
队员1
队员2
队员3
队员4
平均数 x¯ (秒)
51
50
方差s2(秒2)
3.5
14.5
15.5
根据表中数据,要从中选择一名成绩好又发挥稳定的运动员参加比赛,应该选择( )