(1+1/2)+(2+1/4)+…+(n+1/2n)=_.
问题描述:
(1+
)+(2+1 2
)+…+(n+1 4
)=______. 1 2n
答
(1+
)+(2+1 2
)+…+(n+1 4
)1 2n
=(1+2+3+…+n)+(
+1 2
+1 22
+…+1 23
)1 2n
=
+n(n+1) 2
(1−(1 2
)n)1 2 1−
1 2
=
+1−n(n+1) 2
.1 2n
故答案为:
+1−n(n+1) 2
.1 2n