问题:
下列三个命题:①若 |
a
+
b
|=|
a
-
b
|,则
a
•
b
=0; ②若
a
≠
0
,
a
•
b
=
a
•
c
,则
b
=
c
;③若 |
a
•
b
|=|
a
||
b
|,则
a
∥
b
.其中真命题有______.(写出所有真命题的序号)
下列三个命题:①若 |
+
|=|
-
|,则
•
=0; ②若
≠
,
•
=
•
,则
=
;③若 |
•
|=|
||
|,则
∥
.其中真命题有______.(写出所有真命题的序号)
a |
b |
a |
b |
a |
b |
a |
0 |
a |
b |
a |
c |
b |
c |
a |
b |
a |
b |
a |
b |
参考答案: