$$\left. \begin{array} { l } { + B + C = A B C ? } \\ { A . } \\ { - 17 - 3 } \\ { - 7 - 7 } \\ { 6 } \end{array} \right.$$
$B=-C\text{, }C\in \mathrm{R}\text{, }A=0\text{, }a=0\text{, }b=-20\text{, }c=-14\text{, }d=6$
$B=-\frac{C}{1-AC}\text{, }C\in \mathrm{R}\setminus 0,\frac{1}{A}\text{, }A\neq 0\text{, }a=A\text{, }b=-20\text{, }c=-14\text{, }d=6$
$B=0\text{, }C=0\text{, }A\neq 0\text{, }a=A\text{, }b=-20\text{, }c=-14\text{, }d=6$
