设等差数列{an}中,a10=23,a25=—22,Sn为其前几项和,求使Sn
在等差数列an中,a10=23,a25=-22,Sn为前n项和,该数列从第几项开始为负?求Sn
两个高中数列的题1.若{an}是等差数列且an=Sn/(n+c),求非零常数c2.等差数列中,a10=23,a25=-2
在等差数列an中,Sn为前n项和,若a3+a10+a17=60,求S19
设等差数列{an}满足a3=5,a10=-9,Sn是数列{an}的前n项和,则Sn的最大值为______.
已知正向等差数列an中,其前n项和为sn,满足2sn=anan+1,求数列an的通项公式,设bn=sn
设等差数列{an}的前n项和为Sn,若首项a10,S8=S12,则当Sn取得最小值时n的
等差数列an中,公差d>0,且a5+a10=0,记数列-2/an的前n项和为Sn,则使Sn
等差数列{an}的前n项和为Sn,且a10=30,a20=50 (1)求通项an(2)若Sn=242求n
等差数列{an}中,已知a10=30,a20=50,sn=242,求n
已知等差数列an中,a2+a5=19,Sn=40,求a10
设等比数列{an}中,a1=256,前n项和为Sn,且Sn,Sn+2,Sn+1成等差数列,
an的前n项和为Sn,-a1,sn,an+1成等差数列求an 2设bn=1-Sn问是否存在a1,使等差数列bn为等比数列