> 数学 >
1+
1
1+2
+
1
1+2+3
+…+…+
1
1+2+3+…+100
=______
1×2×3+2×4×6+4×8×12+7×14×21
1×3×5+2×6×10+4×12×20+7×21×35
=______.
人气:299 ℃ 时间:2019-08-21 16:05:02
解答
(1)原式=2×(1-
1
2
+
1
2
-
1
3
+…+
1
100
-
1
101
),
=2×(1-
1
101
),
=2×
100
101

=
200
101

(1)原式=
6×(1+2×2×2+2×4×8+7×7×7)
15(1+2×2×2+2×4×8+7×7×7)

=
6
15

=
2
5
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