考虑一个 3 × 3 3times 3 3×3的行列式 M M M
M = ∣ a 11 a 12 a 13 a 21 a 22 a 23 a 31 a 32 a 33 ∣ M=left | begin{array}{ccc} a_{11}&a_{12}&a_{13}\ a_{21}&a_{22}&a_{23}\ a_{31}&a_{32}&a_{33} end{array} right| M=∣∣∣∣∣∣a11a21a31a12a22a32a13a23a33∣∣∣∣∣∣
= a 11 a 22 a 33 + a 12 a 23 a 31 + a 13 a 21 a 32 − a 13 a 22 a 31 − a 11 a 23 a 32 − a 12 a 21 a 33 =a_{11}a_{22}a_{33}+a_{12}a_{23}a_{31}+a_{13}a_{21}a_{32}-a_{13}a_{22}a_{31}-a_{11}a_{23}a_{32}-a_{12}a_{21}a_{33} =a11a22a33+a12a23a31+a13a21a32−a13a22a31−a11a23a32−a12a21a33
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