$V = \dfrac{1}{6} \bigg| [\vec{AB},\vec{AC}].\vec{AD} \bigg|$
Gọi $D(0;a;0) \in Oy. \vec{AB} = (0;2;-4);\ \vec{AC} = (1;1;-2);\ \vec{AD} = (-2;\ a+1;\ -3)$
$[\vec{AB},\vec{AC}] = (0;\ -4;\ -2);\ \ \bigg| [\vec{AB},\vec{AC}].\vec{AD} \bigg| = -2.0 - 4(a+1) + (-2).(-3) = 2 - 4a$
$V = \dfrac{1}{6} |2-4a| = 5 \Rightarrow |2-4a| = 30 \Rightarrow a = 7$ hoặc $a = 8$
Có 2 điểm $D$ thỏa mãn ycbt