Разложите на множители x^2-4x-y^2+4y

[latex]x^2-4x-y^2+4y=\left(x^2-y^2\right)+\left(-4x+4y\right)=\\\\=\left(x^2-y^2\right)-4\left(x-y\right)=(x-y)(x+y)-4(x-y)=\\\\=\left(x-y\right)\left(\left(x+y\right)-4\right)=(x-y)(x+y-4).[/latex]