问题 解答题
观察下列等式:
1
1×2
=1-
1
2
1
2×3
=
1
2
-
1
3
1
3×4
=
1
3
-
1
4
,将以上三个等式两边分别相加得:
1
1×2
+
1
2×3
+
1
3×4
=1-
1
2
+
1
2
-
1
3
+
1
3
-
1
4
=1-
1
4
=
3
4

(1)猜想并写出:
1
n(n+1)
=______;
(2)直接写出下列各式的计算结果:
1
1×2
+
1
2×3
+
1
3×4
+…+
1
2006×2007
=______;
1
1×2
+
1
2×3
+
1
3×4
+…+
1
n(n+1)
=______.
(3)探究并计算:
1
2×4
+
1
4×6
+
1
6×8
+…+
1
2006×2008
答案

(1)

1
n
-
1
n+1

(2)①

2006
2007

n
n+1

(3)原式=

1
2
(
1
2
-
1
4
)+
1
2
(
1
4
-
1
6
)+
1
2
(
1
6
-
1
8
)+…+
1
2
(
1
2006
-
1
2008
)

=

1
2
(
1
2
-
1
4
+
1
4
-
1
6
+
1
6
-
1
8
+…+
1
2006
-
1
2008
)

=

1
2
(
1
2
-
1
2008
)

=

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