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|
=|a1,3a2,2a3|+|b1,3a2,2a3|
=3×2|a1,a2,a3|+3/2×2|b1,2a2,a3|
=6|A|+3|B|
=6×2+3×3
=21