问题
解答题
求数列1
|
答案
由题意可得Sn=1
+31 2
+51 4
+…+(2n-1+1 8
)1 2n
=(1+3+5+…+2n-1)+(
+1 2
+1 4
+…+1 8
)1 2n =
+(1+2n-1)n 2
=n2+1-
[1-(1 2
)n]1 2 1- 1 2 1 2n
搜题请搜索小程序“爱下问搜题”
求数列1
|
由题意可得Sn=1
+31 2
+51 4
+…+(2n-1+1 8
)1 2n
=(1+3+5+…+2n-1)+(
+1 2
+1 4
+…+1 8
)1 2n =
+(1+2n-1)n 2
=n2+1-
[1-(1 2
)n]1 2 1- 1 2 1 2n
