Не знаю как решать
1) x^2 + 9 = (x + 9)^2 x^2 + 9 = x^2 + 18x + 81 9 - 81 = 18x 18x = -72 x = -72/18 = -4 2) (4x^2 + y^2 - (2x - y)^2) : (2xy) = = (4x^2 + y^2 - (4x^2 - 4xy + y^2)) : (2xy) = = (4x^2 + y^2 - 4x^2 + 4xy - y^2)) : (2xy) = = (4xy) : (2xy) = 2