题目内容
已知|
+
|=3，|
-
|=4，则
•
=______．
| a |
| b |
| a |
| b |
| a |
| b |
∵|
+
|=3，|
-
|=4
∴|
+
|2=
2+
2+
•
=9，①
|
-
|2=
2+
2-2
•
=16，②
①-②得4
•
=-7
∴
•
=-
故答案为-
| a |
| b |
| a |
| b |
∴|
| a |
| b |
| a |
| b |
| a |
| b |
|
| a |
| b |
| a |
| b |
| a |
| b |
①-②得4
| a |
| b |
∴
| a |
| b |
| 7 |
| 4 |
故答案为-
| 7 |
| 4 |
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