已知等差数列{an},│a5│=│a9│公差d
问题描述:
已知等差数列{an},│a5│=│a9│公差d
答
│a5│=│a9│公差d0
a5>0 a9
已知等差数列{an},│a5│=│a9│公差d
│a5│=│a9│公差d0
a5>0 a9