Решите систему уравнений: ДАЮ 40 БАЛЛОВ x+y-xy=7 3xy+2(x+y)= -36

$\left \{ {{x+y-xy=7} \atop {3xy+2(x+y)= -36}} \right.$
Замена
$\left \{ {{a=x+y} \atop {b=xy}} \right.$
$\left \{ {{a-b=7} \atop {3b+2a= -36}} \right.$
$\left \{ {{a=b+7} \atop {3b+2(b+7)=-36}} \right.$
$\left \{ {{a=b+7} \atop {5b=-50}} \right.$
$\left \{ {{a=-3} \atop {b=-10}} \right.$
$\left \{ {{x+y=-3} \atop {xy=-10}} \right.$
$\left \{ {{x=-y-3} \atop {y(-y-3)=-10}} \right.$
$\left \{ {{x=-y-3} \atop {y^2+3y+10=0}} \right.$
$D=9+40=49=7^2$
$y_1= \frac{-3+7}{2}=2$
$y_2= \frac{-3-7}{2}=-5$
$\left \{ {{y=2,x=-5} \atop {y=-5, x=2}} \right.$
Ответ: (2;-5), (-5;2)