等比数列an中,a8/a5=-1/27,那么(a1+a3+a5+a9)/(a2+a4+a6+a8+a10)=
问题描述:
等比数列an中,a8/a5=-1/27,那么(a1+a3+a5+a9)/(a2+a4+a6+a8+a10)=
答
由a8/a5=-1/27知:
q³a5/a5=-1/27
q³=-1/27
q = -1/3
所以:
(a1+a3+a5+a7+a9)/(a2+a4+a6+a8+a10)
= (a1+a3+a5+a7+a9)/q(a1+a3+a5+a7+a9)
=1/q
= -3