1/1x2+1/2x3+1/3x4+1/4x5+…+1/99x100.
问题描述:
+1 1x2
+1 2x3
+1 3x4
+…+1 4x5
. 1 99x100
答
+1 1x2
+1 2x3
+1 3x4
+…+1 4x5
,1 99x100
=(1-
)+(1 2
-1 2
)+(1 3
-1 3
)+(1 4
-1 4
)+…+(1 5
-1 99
),1 100
=1-
+1 2
-1 2
+1 3
-1 3
+1 4
-1 4
+…+1 5
-1 99
,1 100
=1-
,1 100
=
.99 100