A=[2,-1,1], B=[1,2,-3];
2A=[4,-2,2], 2B=[2,4,-6];
2A+B=[5,0,-1], A-2B=[0,-5,7].
If dot product:
(2A+B)᛫(A-2B)=0+0-7=-7.
|-7|=7.
If vector product:
(2A+B)᰽(A-2B)=[0-(-1)(-5),-(5)(7)+0,(5)(-5)-0]=[-5,-35,-25].
|[-5,-35,-25]|=√(5²+35²+25²)=√1875=25√3=43.3 approx.