设等差数列{an}的前n项和为Sn,已知(a5-1)^3+2009(a5-1)=1,(a2005-1)^3+2009(a2005-1)=-1,则正确的是A.S2009=2009,a2005小于a5B.S2009=2009,a2005大于a5C.S2009=-2009,a2005小于等于a5D.S2009=-2009,a2005大于等于a5
来源:学生作业帮助网 编辑:作业帮 时间:2024/06/19 02:11:09
![设等差数列{an}的前n项和为Sn,已知(a5-1)^3+2009(a5-1)=1,(a2005-1)^3+2009(a2005-1)=-1,则正确的是A.S2009=2009,a2005小于a5B.S2009=2009,a2005大于a5C.S2009=-2009,a2005小于等于a5D.S2009=-2009,a2005大于等于a5](/uploads/image/z/8783361-9-1.jpg?t=%E8%AE%BE%E7%AD%89%E5%B7%AE%E6%95%B0%E5%88%97%7Ban%7D%E7%9A%84%E5%89%8Dn%E9%A1%B9%E5%92%8C%E4%B8%BASn%2C%E5%B7%B2%E7%9F%A5%EF%BC%88a5-1%29%5E3%2B2009%28a5-1%29%3D1%2C%28a2005-1%29%5E3%2B2009%28a2005-1%29%3D-1%2C%E5%88%99%E6%AD%A3%E7%A1%AE%E7%9A%84%E6%98%AFA.S2009%3D2009%2Ca2005%E5%B0%8F%E4%BA%8Ea5B.S2009%3D2009%2Ca2005%E5%A4%A7%E4%BA%8Ea5C.S2009%3D-2009%2Ca2005%E5%B0%8F%E4%BA%8E%E7%AD%89%E4%BA%8Ea5D.S2009%3D-2009%2Ca2005%E5%A4%A7%E4%BA%8E%E7%AD%89%E4%BA%8Ea5)
设等差数列{an}的前n项和为Sn,已知(a5-1)^3+2009(a5-1)=1,(a2005-1)^3+2009(a2005-1)=-1,则正确的是A.S2009=2009,a2005小于a5B.S2009=2009,a2005大于a5C.S2009=-2009,a2005小于等于a5D.S2009=-2009,a2005大于等于a5
设等差数列{an}的前n项和为Sn,已知(a5-1)^3+2009(a5-1)=1,(a2005-1)^3+2009(a2005-1)=-1,则正确的是
A.S2009=2009,a2005小于a5
B.S2009=2009,a2005大于a5
C.S2009=-2009,a2005小于等于a5
D.S2009=-2009,a2005大于等于a5
设等差数列{an}的前n项和为Sn,已知(a5-1)^3+2009(a5-1)=1,(a2005-1)^3+2009(a2005-1)=-1,则正确的是A.S2009=2009,a2005小于a5B.S2009=2009,a2005大于a5C.S2009=-2009,a2005小于等于a5D.S2009=-2009,a2005大于等于a5
∵等差数列{a[n]}的前n项和为S[n],(a[5]-1)^3+2009(a[5]-1)=1
∴(a[5]-1){(a[5]-1)^2+2009}=1
∵(a[5]-1)^2+2009>0
∴a[5]-1>0
即:a[5]>1
∵(a[2005]-1)^3+2009(a[2005]-1)=-1
∴(a[2005]-1){(a[2005]-1)^2+2009}=-1
∵(a[2005]-1)^2+2009
∴a[2005]-1