等差数列中a3a7=-16 a4+a6=0求an前n项和

问题描述:

等差数列中a3a7=-16 a4+a6=0求an前n项和
应是a4+a5=0

a4+a5=0
a5=-a4
d=a5-a4=-2a4
a3a7
=(a4-d)(a4+3d)=-16
3a4*(-5a4)=-16
a4=16/15
an=96/5-(32/15)nSORRY,题目错了,应是a4+a5=0已经更正了 答案不对么