题目内容
4×5
+5×6
+6×7
+7×8
+8×9
=______.
| 3 |
| 4 |
| 4 |
| 5 |
| 5 |
| 6 |
| 6 |
| 7 |
| 7 |
| 8 |
4×5
+5×6
+6×7
+7×8
+8×9
,
=4×(5+
)+5×(6+
)+6×(7+
)+7×(8+
)+8×(9+
),
=20+3+30+4+42+5+56+6+72+7,
=245.
故答案为:245.
| 3 |
| 4 |
| 4 |
| 5 |
| 5 |
| 6 |
| 6 |
| 7 |
| 7 |
| 8 |
=4×(5+
| 3 |
| 4 |
| 4 |
| 5 |
| 5 |
| 6 |
| 6 |
| 7 |
| 7 |
| 8 |
=20+3+30+4+42+5+56+6+72+7,
=245.
故答案为:245.
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