计算:1/1×4+1/4×7+1/7×10+…+1/2005×2008.
问题描述:
计算:
+1 1×4
+1 4×7
+…+1 7×10
. 1 2005×2008
答
+1 1×4
+1 4×7
+…+1 7×10
1 2005×2008
=
(1-1 3
)+1 4
(1 3
-1 4
)+1 7
(1 3
-1 7
)+…+1 10
(1 3
-1 2005
)1 2008
=
(1-1 3
)1 2008
=
.669 2008