Question

if a+b+c=5 and ab+bc+ca=10 then prove that a cube + b cube + c cube -3abc = -25

Answer 1

if a+b+c =5 ab+BC+ca=10 aCube B cube and c cube ( a+b+c) cube =a cube +bcube+c cube +3ab +3bc+3ca we know that a+b+c= 5 so (5)whole cube. = 3 (ab+BC+ca). 125 =3(10) +3(10 ) = 125-60 =75