Răspuns:
x²+xy+y+x+xy+y²=20
x²+y²+2xy+x+y =20 (voi face prin formulele lui Viete)
S²-2P+2P+S=20 (-2P si 2P se reduc)
S²+S=20
S²+S-20=0
a=1 b=1 c=-20
calculam ∆
∆=b²-4ac=1²-4*1*(-20)=1+80=81=>√∆=√81=9
S1,2= -b±√∆/2a = -1±9/2=>
=>S1=-1-9/2=-10/2=-5
=>S2=-1+9/2=8/2=4
Sper ca te-am ajutat!
