题目内容
计算(7
-5
)
(7
+5
)
=______．
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| 3 |
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| 3 |
原式=[（7
-5
）（7
+5
）]
，
=[（7
）2-（5
）2]
，
=2
，
=
．
故答案为：
．
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| 2 |
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| 2 |
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=[（7
| 1 |
| 2 |
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| 2 |
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=2
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| 3 |
=
| 3 | 2 |
故答案为：
| 3 | 2 |
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