Consider $a^{2}+6ab-c^{2}-6bc$ as a polynomial over variable $a$.
$$a^{2}+6ba-c^{2}-6bc$$
Find one factor of the form $a^{k}+m$, where $a^{k}$ divides the monomial with the highest power $a^{2}$ and $m$ divides the constant factor $-6bc-c^{2}$. One such factor is $a-c$. Factor the polynomial by dividing it by this factor.
