EccentricSW 2020-09-07T13:44:48+00:00 [img]https://img.nga.178.com/attachments/mon_202009/10/-7Q5-jxv7KcT3cSsg-3t.jpg.medium.jpg[/img]这里方阵A只能是零矩阵吗，想不到反例[s:ac:晕]