Question

Помогите решить систему уравнений
x+y=4
xy=4

Answer 1

$left { {{x=4-y} atop {(4y)y=4}} right. left { {{x=4-y} atop {4y-y^2-4=0}} right.$

$left { {{x=4-y} atop {y2-4y+4=0}} right. D=16-16=0,y= frac{4-0}{2}=2, x=4-2=2, (2;2)$