Математика: {x-y=2 {x+yx=20 розвяжите сис-му равнение!

$\left \{ {{x-y=2} \atop {x+yx=20}} \right.$
$\left \{ {{x=2+y} \atop {x+yx=20}} \right. [/tex [tex]2+y+y(2+y) = 20$
$2+3y+ y^{2} = 20$
$D = b^{2} - 4*a*c = 9 - 4*1*2 = 1$
$y1 = \frac{-3-1}{2} = \frac{-4}{2} = -2$
$y2 = \frac{-3+1}{2} = \frac{-2}{2} = -1$
$x1 = 2-2=0$
$x2 = 2-1 = 1$
ОТВЕТ: x1 = 0, y1 = -2 : x2 = 1, y2 = -1