A B三阶方阵 A=(a1 a2 a3)B=(b1 2a2 a3)A|=2 |B|=3 则|A+B|=?
问题描述:
A B三阶方阵 A=(a1 a2 a3)B=(b1 2a2 a3)A|=2 |B|=3 则|A+B|=?
答
|A+B|
= | a1+b1,3a2,2a3|
= 6 |a1+b1,a2,a3|
= 6 ( |a1,a2,a3| + |b1,a2,a3|)
= 6 ( |A| + |b1,2a2,a3|/2)
= 6|A| + 3|B|
= 6*2 + 3*3
= 21.