A-3B=[-2a1,-2a2,-2a3,a-3b]
|A-3B|
=|[-2a1,-2a2,-2a3,a-3b] |
=|[-2a1,-2a2,-2a3,a] |-3|[-2a1,-2a2,-2a3,b]
=(-8)|[a1,a2,a3,a] |+24|[a1,a2,a3,b] |
=-16+72
=56
A-3B=[-2a1,-2a2,-2a3,a-3b]
|A-3B|
=|[-2a1,-2a2,-2a3,a-3b] |
=|[-2a1,-2a2,-2a3,a] |-3|[-2a1,-2a2,-2a3,b]
=(-8)|[a1,a2,a3,a] |+24|[a1,a2,a3,b] |
=-16+72
=56