(x-3y)(x+3y)-x(3x-y)+(3y-x)^
(x-3y)(x+3y)-x(3x-y)+(3y-x)^2 =
= x² - 9y² - 3x² + xy + 9y² - 6xy +x² =
= - x² - 5xy = -x·(x +5y)
(x-3y)(x+3y)-x(3x-y)+(3y-x)^2= =x^2-9y^2-3x^2+xy+9y^2-6xy+x^2 = =-x^2-5xy=-x*(x+5y);