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

x + y = 9xy = - 10x = 9 - yy (9 - y ) + 10 = 0 *9y - y^2 + 10 = 0 - y^2 + 9y +10 = 0 y^2 - 9y - 10 = 0 D = 81 + 40 = 121 = 11^2y1 = ( 9 + 11)/2 = 20/2 = 10;y2 = ( 9 - 11)/2 = - 2/2 = - 1;y1 = 10x1 = 9 - y1 = 9 - 10 = - 1;y2 = - 1x1 = 9 - y2 = 9 + 1 = 10 Ответ( - 1; 10)( 10; - 1)