∵a1,a3,a9 成等比数列
∴a3²=a1×a9
又因为﹛an﹜是等差数列
∴(a1+2d)²=a1(a1+8d)
∴4a1d=4d²
∴d=0或a1=d
(1)d=0时,an=a1
∴(a1+a4+a2)/(a8+a5+a7)
=3a1/3a1=1
(2)a1=d,an=a1+(n-1)d=na1
∴(a1+a4+a2)/(a8+a5+a7)
=(a1+4a1+2a1)/(8a1+5a1+7a1)
=7a1/20a1
=7/20
明教为您解答,
请点击[满意答案];如若您有不满意之处,请指出,我一定改正!
希望还您一个正确答复!
祝您学业进步!