9 класс
(x^2+6x)^2+2(x+3)^2=81

и да спасибо

(x^2 + 6x)^2 + 2(x^2 + 6x + 9) - 81 = 0 x^2 + 6x = a, x^2 +6x + 9 = a + 9, a^2 + 2(a + 9) - 81 = 0, a^2 + 2a - 63 = 0 а1 = -9 a2 = 7 x^2 + 6x = -9 x^2 + 6x + 9 = 0 x = -3 x^2 + 6x = 7 x^2 + 6x -7 = 0 x1 = -7 x2 = 1 ответ. -7; -3; 1.