问题描述: 等差数列an中,公差为d(不等于0),且a1,a3,a9成等比数列,则(a1+a3+a9)/(a2+a4+a9)的值为 1个回答 分类:数学 2014-12-15 问题解答: 我来补答 a3=a1+2da9=a1+8da1a9=a3^2a1*(a1+8d)=a1^2+8a1d(a1+2d)^2=a1^2+4a1d+4d^2a1^2+8a1d=a1^2+4a1d+4d^2(a1-d)d=0因为d不等于0a1=d(a1+a3+a9)/(a2+a4+a9)=(a1+3a1+9a1)/(2a1+4a1+9a1)=13a1/15a1=13/15 展开全文阅读