X+y=9 xy=-10 система квадратных уравнений

X + y = 9

xy = - 10

x = 9 - y

y (9 - y) + 10 = 0 *

9y - y^2 + 10 = 0

- y^2 + 9y + 10 = 0

y^2 - 9y - 10 = 0

D = 81 + 40 = 121 = 11^2

y1 = (9 + 11) / 2 = 20/2 = 10;

y2 = (9 - 11) / 2 = - 2/2 = - 1;

y1 = 10

x1 = 9 - y1 = 9 - 10 = - 1;

y2 = - 1

x1 = 9 - y2 = 9 + 1 = 10

Ответ

(- 1; 10)

(10; - 1)