设a ,b,r1,r2,r3都是4维列向量,A=|a,r1,r2,r3|=5,B=|b,r1,r2,r3|=-1,则|A+B|=?

|A+B|
= |a+b,2r1,2r2,2r3|
= 8 |a+b,r1,r2,r3|
= 8 (|a,r1,r2,r3|+|b,r1,r2,r3|)
= 8 (5 - 1)
= 8*4
= 32.需注意矩阵的加法与行列式的分拆的区别 矩阵加法 A+B = (a+b,2r1,2r2,2r3)是的, 没错呀 矩阵加法 A+B = (a+b,2r1,2r2,2r3) |A+B| = |a+b,2r1,2r2,2r3|这是矩阵和的行列式是的