AB(5,-3,-2) CD(-2,6,-5) 2AB=2(5,-3,-2)=(10,-6,-4) 3CD=3(-2,6,-5)=(-6,18,-15) I2AB + 3CDI=(10+(-6),-6+18,-15+(-4))=(4,12,-19) √4^2+12^2+(-19^2)=√16+144+361=√521