早教吧作业答案频道 -->数学-->
两等差数列{an}.{bn}的前n项和的比Sn/S'n=5n+3/2n+7,则a5/b5的值是?
题目详情
两等差数列{an}.{bn}的前n项和的比Sn/S'n=5n+3/2n+7,则a5/b5的值是?
▼优质解答
答案和解析
a5/b5
=(a5+a5)/(b5+b5)
=(a1+a9)/(b1+b9)
=[(a1+a9)×9÷2]/[(b1+b9)×9÷2]
=S9/S'9
=(5×9+3)/(2×9+7)
=48/25
=(a5+a5)/(b5+b5)
=(a1+a9)/(b1+b9)
=[(a1+a9)×9÷2]/[(b1+b9)×9÷2]
=S9/S'9
=(5×9+3)/(2×9+7)
=48/25
看了 两等差数列{an}.{bn}...的网友还看了以下：