Решите системное уровнение {X^2-y=21 {X+y=9
Сложим x^2 + x = 30 x^2 + x - 30 = 0 D = 1 + 4*30 = 121 x1 = ( - 1 + 11)/2 = 5 x2 = ( - 1 - 11)/2 = - 6 x1 = 5 y1 = 9 - x1 = 9 - 5 = 4 x2 = - 6 y2 = 9 - x1 = 9 + 6 = 15 Ответ ( 5; 4) ; ( - 6; 15)