Lời giải:Đường thẳng \(\left( {{d_m}} \right)//d \Leftrightarrow \left\{ \begin{array}{l}{m^2} + m - 4 = 2\\m - 7 \ne - 5\end{array} \right.\)
\(\begin{array}{l} \Leftrightarrow \left\{ \begin{array}{l}{m^2} + m - 6 = 0\\m \ne 2\end{array} \right. \\\Leftrightarrow \left\{ \begin{array}{l}\left( {m - 2} \right)\left( {m + 3} \right) = 0\\m \ne 2\end{array} \right.\\ \Leftrightarrow \left\{ \begin{array}{l}\left[ \begin{array}{l}m - 2 = 0\\m + 3 = 0\end{array} \right.\\m \ne 2\end{array} \right.\\ \Leftrightarrow \left\{ \begin{array}{l}\left[ \begin{array}{l}m = 2\\m = - 3\end{array} \right.\\m \ne 2\end{array} \right. \Leftrightarrow m = - 3.\end{array}\)
Vậy \(m = - 3\)
