|A+B|=|A1+B1,2A2,2A3,2A4|(本来行列式没逗号,为了方便你看)提取第2、3、4行的2得
|A+B|=8|A1+B1,A2,A3,A4|运用公式,拆开
=8|A1,A2,A3,A4|+8|B1,A2,A3,A4|
=8|A|+8|B|=8*(-3)+8*2=-8
|A+B|
= | A1+B1,A2,A3,A4|
= | A1,A2,A3,A4| + | B1,A2,A3,A4| --行列式的性质: 分拆
= |A| + |B|
= -3 + 2
= -1.