已知数列{bn]的通项公式bn=2n-31求数列{/bn/}的前n项和Tn

问题描述:

已知数列{bn]的通项公式bn=2n-31求数列{/bn/}的前n项和Tn

bn=2n-31
∴Tn=2×1-31+2×2-31+……+2n-31
=2×(1+2+……+n)-31n
=n(n+1)-31n
=n^2-30n