OI-WIKI 上说 正确性证明需要用到较多线性代数的知识，我觉得有更简洁的证法。
by phoenixzhan @ 2023-03-28 19:36:42
这俩等价的。
by esquigybcu @ 2023-03-28 19:44:13
https://math.stackexchange.com/questions/1102465/why-is-the-left-inverse-of-a-matrix-equal-to-the-right-inverse
by esquigybcu @ 2023-03-28 19:45:50
神奇！
by phoenixzhan @ 2023-03-28 19:54:57
@[_CCF](/user/758679) 一个群的左右逆元相等
by Untitled0 @ 2023-03-28 20:02:43
@[Untitled0](/user/393767) 不会群论
by phoenixzhan @ 2023-03-28 20:03:59