If A-B = 2, B-C = 1, then a & # 178; + B & # 178; + C & # 178; - AB BC AC= Hurry!

If A-B = 2, B-C = 1, then a & # 178; + B & # 178; + C & # 178; - AB BC AC= Hurry!

a-c=a-b+b-c=3
a²+b²+c²-ab-bc-ac=1/2[(a-b)²+(b-c)²+(a-c)²]=1/2(4+1+9)=7