\(\overrightarrow{AC}=\left(3; -4; 4\right), \overrightarrow{AD}=\left(5; 4; 5\right), \overrightarrow{AB}=\left(1; m-2; -1\right), \left[\overrightarrow{AC},\overrightarrow{AD}\right]=\left(-36; 5; 32\right) \)
\(A,{\rm }B,{\rm }C,{\rm }D \) đồng phẳng \(\Leftrightarrow \overrightarrow{AC}, \overrightarrow{AD}, \overrightarrow{AB}\) đồng phẳng \(\Leftrightarrow \left[\overrightarrow{AC},\overrightarrow{AD}\right].\overrightarrow{AB}=0 \)
\(\Leftrightarrow -36+5(m-2)-32=0\Leftrightarrow m=\frac{78}{5} . \)