=(1;-1;-5)
2*vector{AB}=2*(1;-1;-5)=(2;-2;-10)
vector{BC}=(x_(C)-x_(B);y_(C)-y_(B); z_(C)-z_(B))=(1-3;-2-0;0-(-1))=
=(-2;-2;1)
3*vector{BC}=3*(-2;-2;1)=(-6;-6;3)
2*vector{AB}+3*vector{BC}=(2;-2;-10)+(-6;-6;3)=(2+(-6);-2+(-6);-10+3)=
=(-4;-4;-7)