【導(dǎo)讀】1.已知等差數(shù)列{an}滿足9aa2aa832823???,且an<0,則其前10項(xiàng)之和為()。5.等差數(shù)列{an}的公差d?0,且a1,a3,a9成等比數(shù)列,則。7.一個(gè)等差數(shù)列的前12項(xiàng)和為354,前12項(xiàng)中,偶數(shù)項(xiàng)和與奇數(shù)項(xiàng)和之比為32:27,8.若等比數(shù)列{an}滿足an>0,(n?N﹡),公比q=2,且a1a2…9.在等差數(shù)列{an}中,若a10=0,則有等式a1+a2+…為等差數(shù)列,試求?11.設(shè){an}是等差數(shù)列,12.設(shè)數(shù)列{an}的首項(xiàng)a1=1,前n項(xiàng)和Sn滿足關(guān)系式3tSn-Sn-1=3t(t>0,n=2,3,4,…