此处 2a13 A=a21a22a23=a13+a2a23a31+a3a21a32 31 13a22431-412c21a33-411a23c32 C 23 a21a23 21 22 32a33 31433 32 =a1141+a12412+a13413 (8) 其中A1,A12,A13为△的代数余子式此处 31 32 33 21 22 23 11 12 13 a a a a a a a a a  = = a11a22 a33 + a12 a23a31 + a13a21a32 − a13a22a31 − a12a21a33 − a11a23a32 32 33 22 23 11 a a a a = a 31 33 21 23 12 a a a a − a 31 32 21 22 13 a a a a + a . = a11A11 + a12 A12 + a13A13 (8) 其中A11, A12，A13为的代数余子式