2/3+2/9+2/27+2/81+2/243.
问题描述:
+2 3
+2 9
+2 27
+2 81
. 2 243
答
+2 3
+2 9
+2 27
+2 81
2 243
=1-
+1 3
-1 3
+1 9
-1 9
+1 27
-1 27
+1 81
-1 81
1 243
=1-
1 243
=
242 243