x^3 - y^3 + 5x(x^2 + xy + y^2)

(x - y)(x^2 + xy + y^2) + 5x(x^2 + xy + y^2)

(x - y + 5x)(x^2 + xy + y^2)

(x + 4x - y)(x^2 + xy + y^2)

(5x - y)(x^2 + xy + y^2)