Let f be a polynomial which has roots a, b, c, we have f(t)=(t−a)(t−b)(t−c) = t3
− (a+b+c)t2
+(ab+bc+ca)t−abc. If a + b + c = 1 then we have f(t)=(t−a)(t−b)(t−c) = t3
−t
2
+(ab+bc+ca)t −
abc. Taking into account the inequality C-B-S one obtains t
3
−t
2
+(ab+bc+ca)t−abc ≤