题目内容
观察下列等式
=1-
,
=
-
,
=
-
,将以上三个等式两边分别相加得:
+
+
=1-
+
-
+
-
=1-
=
.
(1)猜想并写出:
=______.
(2)直接写出下列各式的计算结果:
①
+
+
+…+
=______;
②
+
+
+…+
=______.
(3)探究并计算:
+
+
+…+
.
1 |
1×2 |
1 |
2 |
1 |
2×3 |
1 |
2 |
1 |
3 |
1 |
3×4 |
1 |
3 |
1 |
4 |
1 |
1×2 |
1 |
2×3 |
1 |
3×4 |
1 |
2 |
1 |
2 |
1 |
3 |
1 |
3 |
1 |
4 |
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 |
1×2 |
1 |
2×3 |
1 |
3×4 |
1 |
2012×2013 |
②
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 |
2012×2014 |
(1)
-
;
(2)①原式=1-
+
-
+
-
+…+
-
=1-
=
;
②原式═1-
+
-
+
-
+…+
-
=1-
=
;
(3)原式=
(
+
+
+…+
)
=
(1-
)
=
.
故答案为
-
;
;
.
1 |
n |
1 |
n+1 |
(2)①原式=1-
1 |
2 |
1 |
2 |
1 |
3 |
1 |
3 |
1 |
4 |
1 |
2012 |
1 |
2013 |
1 |
2013 |
2012 |
2013 |
②原式═1-
1 |
2 |
1 |
2 |
1 |
3 |
1 |
3 |
1 |
4 |
1 |
n |
1 |
n+1 |
1 |
n+1 |
n |
n+1 |
(3)原式=
1 |
4 |
1 |
1×2 |
1 |
2×3 |
1 |
3×4 |
1 |
1006×1007 |
=
1 |
4 |
1 |
1007 |
=
503 |
2014 |
故答案为
1 |
n |
1 |
n+1 |
2012 |
2013 |
n |
n+1 |
练习册系列答案
相关题目