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

问题描述:

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

15,由题意得a5=-a10,可以得到-2/a5=2/a10,即-2/a5+(-2/a10)=0,同理可a1和a14,a2和a13也是这样.