题目内容：
已知向量a=(1,-1)，b=(2,x)。若a•b=1,则x=
A．(A)-1 B．(B)-(1/2)
C．(C)1/2
D．(D)1
参考答案：
答案解析：
单选题：已知向量a=(1,-1)，b=(2,x)。若a•b=1,则x=
- 题目分类：数学(文科)
- 题目类型：单选题
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B．(B)-(1/2)
C．(C)1/2
D．(D)1
B．(B)-(1/2)
C．(C)1/2
D．(D)1
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