Consider $x^{2}-y^{2}-4x-2y+3$ as a polynomial over variable $x$.
$$x^{2}-4x-y^{2}-2y+3$$
Find one factor of the form $x^{k}+m$, where $x^{k}$ divides the monomial with the highest power $x^{2}$ and $m$ divides the constant factor $-y^{2}-2y+3$. One such factor is $x+y-1$. Factor the polynomial by dividing it by this factor.
