b-a=1c-b=1c-a=2a²+b²+c²-ab-ac-bc=(1/2)(a²-2ab+b²+b²-2bc+c²+c²-2bc+a²)=(1/2)[(b-a)²+(c-b)²+(c-a)²]=(1/2)(1²+1²+2²)=6/2=3