问题
解答题
裂项相消法:求数列
|
答案
设an=
=1
+n n+1
-n+1
(裂项)n
则 Sn=
+1 1+ 2
+…+1
+2 3 1
+n n+1
=(
-1)+(2
-3
)+…+(2
-n+1
) (裂项求和)n
=
-1n+1
裂项相消法:求数列
|
设an=
=1
+n n+1
-n+1
(裂项)n
则 Sn=
+1 1+ 2
+…+1
+2 3 1
+n n+1
=(
-1)+(2
-3
)+…+(2
-n+1
) (裂项求和)n
=
-1n+1