等差数列AN,公差D不等于0,A1,A2,A3,A4等比数列,则(A1+A5+A17)/(A2+A6+A18)=?
收藏:
0
点赞数:
0
评论数:
0
2个回答

是A1,A3,A4等比数列吧?

∵A1,A3,A4等比数列

∴(a3)²=(a1)×(a4)

(a1+2d)²=(a1)(a1+3d)

a²₁+4d²+4a1d=a²₁+3a1d

4a1d+4d²=3a1d

a1d+4d²=0

d(a1+4d)=0

∵d≠0

∴a1+d=0 即a1=-4d

(A1+A5+A17)/(A2+A6+A18)

=(A1+A1+4d+A1+16d)/(A1+d+A1+5d+A1+17d)

=(3A1+20d)/(3A1+23d)

=(-12d+20d)/(-12d+23d)

=8f/11d

=8/11

点赞数:
0
评论数:
0
关注公众号
一起学习,一起涨知识