x³=-x²+4x-6 pt∀x∈R
atunci in particular
xi=-xi²+4xi-6 unde i=1;2;3 adica radacinile polinomului
notand cu Sk= x1^k+x2^k+x3^k si
insumand, obtinem
S3= -S2+4S1-18 (1)
S1= (Viete)=-1
S2=S1²-2(x1x2+x2x3+x3x1)=1-2*(-4)=1+8=9
si atunci relatia (1) devine:
S3=-9+4(-1)-18=-9-22=-31
