题目内容
计算
1
+2
+…+51
.
1
| 2 |
| 9×10 |
| 2 |
| 10×11 |
| 2 |
| 59×60 |
1
+2
+…+51
,
=(1+2+3+…+51)+(
+
+…+
),
=(1+51)×51÷2+2×(
-
+
-
+…+
-
),
=1326+2×(
-
),
=1326+
,
=1326+
.
| 2 |
| 9×10 |
| 2 |
| 10×11 |
| 2 |
| 59×60 |
=(1+2+3+…+51)+(
| 2 |
| 9×10 |
| 2 |
| 10×11 |
| 2 |
| 59×60 |
=(1+51)×51÷2+2×(
| 1 |
| 9 |
| 1 |
| 10 |
| 1 |
| 10 |
| 1 |
| 11 |
| 1 |
| 59 |
| 1 |
| 60 |
=1326+2×(
| 1 |
| 9 |
| 1 |
| 60 |
=1326+
| 17 |
| 90 |
=1326+
| 17 |
| 90 |
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