若数列an的前n项和Sn=n^2-10n,则数列通项为?
问题描述:
若数列an的前n项和Sn=n^2-10n,则数列通项为?
RT
答
an=sn-S(n-1)=n^2-10n-【(n-1)^2-10(n-1)】=2n-11
若数列an的前n项和Sn=n^2-10n,则数列通项为?
RT
an=sn-S(n-1)=n^2-10n-【(n-1)^2-10(n-1)】=2n-11