Consider $-x^{3}-y^{3}$ as a polynomial over variable $x$. Find one factor of the form $kx^{m}+n$, where $kx^{m}$ divides the monomial with the highest power $-x^{3}$ and $n$ divides the constant factor $-y^{3}$. One such factor is $x+y$. Factor the polynomial by dividing it by this factor.
