【一分钟搞定大学数学】矩阵8-判断正定二次型-顺序主子式-超详细解答
https://www.bilibili.com/video/BV11T4y1S7YF/?spm_id_from=333.337.search-card.all.click&vd_source=f911c2c08bf9fde8550390cc7145f5f3

https://www.bilibili.com/video/BV11T4y1S7YF/?spm_id_from=333.337.search-card.all.click&vd_source=f911c2c08bf9fde8550390cc7145f5f3
