A:狗的长毛与黑毛
B:人的身高和体重
C:圆滑的豌豆和皱缩的豌豆
D:豌豆的高茎和蚕豆的矮茎
锻炼时间x(分钟)
频数
频率
30≤x<40
5
0.10
40≤x<50
10
a
50≤x<60
20
0.40
60≤x<70
b
0.24
70≤x<80
2
0.04
80≤x<90
1
0.02
合计
c
1.00
已知正项等比数列an满足a7=a6+2a5.若存在两项am,an使得aman=4a1,1m+4n的最小值为( )
While ____ the dog, you were careless and it got ____ and was hit by a car.
计算: