a^2+b^2+c^2-ab-bc-ca=0 2a^2+2b^2+2c^2-a2b-2bc-2ca=0 (a-b)^2+(b-c)^2+(a-c)^2=0 a+2b+3c=12 a=b=c=2 a+b^2+c^3=14