问题:
已知向量
a
,
b
,
c
满足
a
-
b
+2
c
=
0
,且
a
⊥
c
,|
a
|=2,|
c
|=1,则|
b
|=______.
已知向量
,
,
满足
-
+2
=
,且
⊥
,|
|=2,|
|=1,则|
|=______.
a |
b |
c |
a |
b |
c |
0 |
a |
c |
a |
c |
b |
参考答案: