Proof WritingHardDirect Proof ShareDirect Proof · Hard problemTo prove a2+b2+c2≥ab+bc+caa^2 + b^2 + c^2 \ge ab + bc + caa2+b2+c2≥ab+bc+ca, one writes 2(a2+b2+c2−ab−bc−ca)=(a−b)2+(b−c)2+(c−a)22(a^2 + b^2 + c^2 - ab - bc - ca) = (a - b)^2 + (b - c)^2 + (c - a)^22(a2+b2+c2−ab−bc−ca)=(a−b)2+(b−c)2+(c−a)2. Exactly when does equality hold?Aa+b+c=0a + b + c = 0a+b+c=0Babc=0abc = 0abc=0Ca=ba = ba=b or b=cb = cb=cDa=b=ca = b = ca=b=cCheck Show answer Walk through it step by step Practice more like this Review this concept