$$A = - 3 a b - 6 b + 15 a b c - 12 a b ^ { 2 }$$
$\left\{\begin{matrix}a=\frac{A+6b}{3b\left(-4b+5c-1\right)}\text{, }&b\neq \frac{5c-1}{4}\text{ and }b\neq 0\\a\in \mathrm{R}\text{, }&\left(A=0\text{ and }b=0\right)\text{ or }\left(A=\frac{3-15c}{2}\text{ and }b=\frac{5c-1}{4}\right)\end{matrix}\right.$
$A=3b\left(-4ab+5ac-a-2\right)$
