早教吧 育儿知识 作业答案 考试题库 百科 知识分享

已知等差数列AN的公差为d,且a1a9=a3*a3,求a1+a3+a9/a2+a4+a10

题目详情
已知等差数列AN的公差为d,且a1a9=a3*a3,求a1+a3+a9/a2+a4+a10
▼优质解答
答案和解析
a1a9=a3a3
a1(a1+8d)=(a1+2d)(a1+2d)
a1²+8a1d=a1²+4a1d+4d²
a1=d
(a1+a3+a9)/(a2+a4+a10)
=(a1+a1+2d+a1+8d)/(a1+d+a1+3d+a1+9d)
=13d/16d
=13/16