Đáp án:
28B, 29D, 30A, 31C
Giải thích các bước giải:
\(\begin{array}{l}
28)\overrightarrow {{u_d}} = \left( {2; - 3;1} \right),\overrightarrow {{n_\beta }} = \left( {1;1; - 1} \right)\\
\Rightarrow \overrightarrow {{n_\alpha }} = \left[ {\overrightarrow {{u_d}} ,\overrightarrow {{n_\beta }} } \right] = \left( {2;3;5} \right)\\
pt\left( \alpha \right):2x + 3\left( {y + 2} \right) + 5\left( {z - 3} \right) = 0\\
\Leftrightarrow 2x + 3y + 5z - 9 = 0\\
29)M\left( {x;0;0} \right) \in \left( P \right)\\
\Rightarrow 2x - 4 = 0 \Rightarrow x = 2 \Rightarrow M\left( {2;0;0} \right)\\
30)pt\left( \alpha \right):\frac{x}{5} + \frac{y}{4} + \frac{z}{3} = 1\\
\Leftrightarrow 12x + 15y + 20z - 60 = 0\\
31)\overrightarrow {AB} = \left( { - 8;6;1} \right)\\
\overrightarrow {{n_\alpha }} = \left[ {\overrightarrow {AB} ;\overrightarrow a } \right] = \left( {5;9; - 14} \right)\\
pt\left( \alpha \right):5\left( {x + 3} \right) + 9\left( {y - 4} \right) - 14\left( {z - 1} \right) = 0\\
\Leftrightarrow 5x + 9y - 14z - 7 = 0
\end{array}\)
