c: \(\left\{{}\begin{matrix}x-3y-z=-6\\2x-y+2z=6\\4x-7y=-6\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}4x-12y-4z=-24\\4x-2y+4z=12\\4x-7y=-6\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}-10y-8z=-36\\-5y-4z=-18\\4x-7y=-6\end{matrix}\right.\Leftrightarrow\left(x,y,z\right)\in R\)
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