题目内容
探究:观察下列各式
=1-
,
=
-
,
=
-
,…请你根据以上式子的规律填写:
+
+
+
+…+
=
;
+
+
…+
=
.
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 |
4×5 |
1 |
2010×2011 |
2010 |
2011 |
2010 |
2011 |
1 |
1×3 |
1 |
3×5 |
1 |
5×7 |
1 |
(2n-1)(2n+1) |
n |
2n+1 |
n |
2n+1 |
分析:利用已知各式的规律将所求式子变形,抵消后通分并利用同分母分式的减法法则计算即可得到结果.
解答:解:
+
+
+
+…+
=1-
+
-
+…+
-
=1-
=
;
+
+
+…+
=
(1-
+
-
+…+
-
)
=
(1-
)
=
.
故答案为:
;
.
1 |
1×2 |
1 |
2×3 |
1 |
3×4 |
1 |
4×5 |
1 |
2010×2011 |
=1-
1 |
2 |
1 |
2 |
1 |
3 |
1 |
2010 |
1 |
2011 |
=1-
1 |
2011 |
2010 |
2011 |
1 |
1×3 |
1 |
3×5 |
1 |
5×7 |
1 |
(2n-1)(2n+1) |
=
1 |
2 |
1 |
3 |
1 |
3 |
1 |
5 |
1 |
2n-1 |
1 |
2n+1 |
=
1 |
2 |
1 |
2n+1 |
=
n |
2n+1 |
故答案为:
2010 |
2011 |
n |
2n+1 |
点评:此题考查了分式的加减法,分式加减运算的关键是通分,通分的关键是找最简公分母.弄清题中的规律是解本题的关键.
练习册系列答案
相关题目