Помогите (Знак системы) x-y=3 x^3-y^3=117

$\left \{ {{x-y=3} \atop {x ^{3}-y ^{3} =117}} \right. \Rightarrow \left \{ {{x-y=3} \atop {(x-y)(x^{2} +xy+y ^{2}) =117}} \right. \Rightarrow \left \{ {{y=x-3} \atop {3( x^{2} +xy+y ^{2}) =117}} \right.$
$\left \{ {{y=x-3} \atop { x^{2} +x(x-3)+(x-3) ^{2} =39}} \right.$
Решаем второе уравнение
х²+х²-3х+х²-6х+9=39,
3х²-9х-30=0
х²-3х-10=0
D=(-3)²-4·(-10)=9+40=49=7²
x₁=(3-7)/2=-2 x₂=(3+7)/2=5
y₁=x₁-3=-2-3=-5 y₂=x₂-3=5-3=2
Ответ (-2;-5) (5;2)