A:①②③④
B:②③④
C:①②④
D:①②③
设e1→,e2→是两个不共线的向量,AB→=2e1→+ke2→,CB→=e1→+3e2→,CD→=2e1→-e2→若A、B、D三点共线,求k的值.
英国最早使用机器生产的部门是( )
根据图表信息,补全对话
1. Q: When is Gina Brown's birthday?
A: ____
2. Q: ____
A: She is 12 years old.
3. Q: Is David Green's birthday on July 12th?
4. Q: ____
A: His birthday is on October 22nd.
5. Q: What's his age?
A: ____
如图,下面是按照一定规律画出的“树形图”,经观察可以发现:图A2比图A1多出2个“树枝”,图A3比图A2多出4个“树枝”,图A4比图A3多出8个“树枝”,…,照此规律,图A6比图A2多出“树枝”( )