等差数列{An},A1004+A1005+A1006+A1007+A1008=10则S2011=

问题描述:

等差数列{An},A1004+A1005+A1006+A1007+A1008=10则S2011=

A1004+A1005+A1006+A1007+A1008=10 数列An为等差数列,则: A1004+A1008=A1005+A1007=2A1006 即5A1006=10 A1006=2 而A1+A2011=2A1006=4 S2011=2011(A1+A2011)/2=4022