分析(1)利用等差数列的通项公式及前n项和公式将已知条件a2=3,S5=25用首项及公差表示,列出方程组求出首项及公差,利用等差数列的通项公式求出通项;(2)将an代入bn,利用等比数列的前n项和公式,注意对x讨论,求出数列{bn}的前n项和Tn;(3)将an代入bn,利用数列的求和方法:错位相减法,化简整理,即可得到Gn. ...
Engineering suppliers have hailed a major milestone in fair payment practice, after it emerged that £10bn of roads work has gone through project bank accounts over the last three years. Highways England revealed that payment for £10.4.bn of work had been made since 2012. Project bank acco...