Question

Помогите решить систему
x+y=9
xy=8

Answer 1

$left { {{y=9-x} atop {xy=8}} right.$ ⇔$left { {{y=9-x} atop {9x- x^{2} =8}} right.$ ⇒ $left { {{y=9-x} atop { x^{2} -9x+8=0}} right.$ ⇔ $left { {{y=8; 1} atop {x=1; 8}} right.$
Ответ: (1;8), (8;1).

Answer 2

х=9-у
(9-у)*у=8
9у-у2-8=0

-у2+9у-8=0

Д=81-32=49

У1= (-9+7): (-2)=1

У2=(-9-7): (-2)= 8

Х1=9-1=8

Х2=9-8=1