-1,5,-7,17,( ),65...按规律填出括号内数字

问题描述:

-1,5,-7,17,( ),65...按规律填出括号内数字

-31
分析:后一项-前一项
5-(-1)=6 = 6×1
-7-5=-12 = 6×(-2)
17-(-7)=24 = 6×4
x-17=-48 = 6×(-8)
所以这个数是-31