问题 选择题
已知函数f(x)=
2x-3,x>1
x+1,0≤x≤1
2x+1,x<0
,若数列{an}的前n项和为Sn,且a1=
1
3
,an+1=f(an),则S2014=(  )
A.895B.896C.897D.898
答案

∵a1=

1
3
,an+1=f(an),且函数f(x)=
2x-3,x>1
x+1,0≤x≤1
2x+1,x<0

∴a2=f(a1)=f(

1
3
)=
1
3
+1=
4
3

a3=f(a2)=f(

4
3
)=
4
3
-3=-
1
3

a4=f(a3)=f(-

1
3
)=2×(-
1
3
)+1
=
1
3
=a1

∴an+3=an

∵a1+a2+a3=

1
3
+
4
3
-
1
3
=
4
3
=a2+a3+a4=….

∴S2014=a1+671(a2+a3+a4

=

1
3
+671×
4
3
=895.

故选:A.

单项选择题
单项选择题