(x+9y)^2 - (9x+y)^2 = (x+9y + 9x + y)(x+9y - 9x - y) = (10x + 10y)(-8x + 8y) = -80x^2 + 80y^2
Правильный ответ: -80x^2 + 80y^2
(x+9y)^2 - (9x+y)^2 = (x+9y + 9x + y)(x+9y - 9x - y) = (10x + 10y)(-8x + 8y) = -80x^2 + 80y^2
Правильный ответ: -80x^2 + 80y^2