一、题目
已知:
$$
\begin{aligned}
D & = \begin{vmatrix}
a_{11} & a_{12} & a_{13} \\
a_{21} & a_{22} & a_{23} \\
a_{31} & a_{32} & a_{33}
\end{vmatrix} \\ \\
D_{1} & = \begin{vmatrix}
2 a_{11} & 2 a_{12} & 2 a_{13} \\
2 a_{21} & 2 a_{22} & 2 a_{23} \\
2 a_{31} & 2 a_{32} & 2 a_{33}
\end{vmatrix}
\end{aligned}
$$
则:
$$
D_{1} = ?
$$
[A]. $2 D$
[C]. $2^{9} D$
[B]. $2^{3} D$
[D]. $2 \cdot 3 D$
难度评级:
二、解析
首先,行 列 式 具有下面的性质:
行 列 式 的某一行(列)中所有的元素都乘以同一数 $k$, 等于用数 $k$ 乘此 行 列 式 。
也就是说,在提取 行 列 式 中元素的系数时,要以 行 或者 列 为单位提取,即:
$$
\begin{aligned}
\begin{rcases}
\begin{vmatrix}
1 \cdot \textcolor{orange}{k_{1}} \cdot \alpha_{1} & 2 \cdot \textcolor{orange}{k_{1}} \cdot \alpha_{2} \\
5 \cdot \textcolor{springgreen}{k_{2}} \cdot \alpha_{3} & 7 \cdot \textcolor{springgreen}{k_{2}} \cdot \alpha_{4}
\end{vmatrix} \\ \\
\begin{vmatrix}
1 \cdot \textcolor{orange}{k_{1}} \cdot \alpha_{1} & 2 \cdot \textcolor{springgreen}{k_{2}} \cdot \alpha_{2} \\
5 \cdot \textcolor{orange}{k_{1}} \cdot \alpha_{3} & 7 \cdot \textcolor{springgreen}{k_{2}} \cdot \alpha_{4}
\end{vmatrix}
\end{rcases} = \textcolor{orange}{k_{1}} \cdot \textcolor{springgreen}{k_{2}} \cdot \begin{vmatrix}
1 \cdot \alpha_{1} & 2 \cdot \alpha_{2} \\
5 \cdot \alpha_{3} & 7 \cdot \alpha_{4}
\end{vmatrix}
\end{aligned}
$$
于是:
$$
\begin{aligned}
D_{1} \\ \\
= & \ \begin{vmatrix}
\textcolor{black}{\colorbox{orange}{2}} a_{11} & \textcolor{black}{\colorbox{orange}{2}} a_{12} & \textcolor{black}{\colorbox{orange}{2}} a_{13} \\
\textcolor{white}{\colorbox{green}{2}} a_{21} & \textcolor{white}{\colorbox{green}{2}} a_{22} & \textcolor{white}{\colorbox{green}{2}} a_{23} \\
\textcolor{brown}{\colorbox{yellow}{2}} a_{31} & \textcolor{brown}{\colorbox{yellow}{2}} a_{32} & \textcolor{brown}{\colorbox{yellow}{2}} a_{33}
\end{vmatrix} \\ \\
= & \ \begin{vmatrix}
\textcolor{black}{\colorbox{orange}{2}} a_{11} & \textcolor{white}{\colorbox{green}{2}} a_{12} & \textcolor{brown}{\colorbox{yellow}{2}} a_{13} \\
\textcolor{black}{\colorbox{orange}{2}} a_{21} & \textcolor{white}{\colorbox{green}{2}} a_{22} & \textcolor{brown}{\colorbox{yellow}{2}} a_{23} \\
\textcolor{black}{\colorbox{orange}{2}} a_{31} & \textcolor{white}{\colorbox{green}{2}} a_{32} & \textcolor{brown}{\colorbox{yellow}{2}} a_{33}
\end{vmatrix} \\ \\
= & \ \textcolor{black}{\colorbox{orange}{2}} \cdot \textcolor{white}{\colorbox{green}{2}} \cdot \textcolor{brown}{\colorbox{yellow}{2}} \cdot D \\ \\
= & \ \textcolor{springgreen}{\boldsymbol{ 2^{3} D }}
\end{aligned}
$$
综上可知,本 题 应 选 B
拓展资料
对于 矩 阵 而言,矩 阵 乘以一个系数 $\textcolor{white}{\colorbox{magenta}{k}}$, 等于 矩 阵 中的每一个元素(而不是某一行或者某一列中的元素)都乘以系数 $\textcolor{white}{\colorbox{magenta}{k}}$:
$$
\textcolor{white}{\colorbox{magenta}{k}} \cdot \begin{bmatrix}
a_{11} & a_{12} & a_{13} \\
a_{21} & a_{22} & a_{23} \\
a_{31} & a_{32} & a_{33}
\end{bmatrix} = \begin{bmatrix}
\textcolor{white}{\colorbox{magenta}{k}} \cdot a_{11} & \textcolor{white}{\colorbox{magenta}{k}} \cdot a_{12} & \textcolor{white}{\colorbox{magenta}{k}} \cdot a_{13} \\
\textcolor{white}{\colorbox{magenta}{k}} \cdot a_{21} & \textcolor{white}{\colorbox{magenta}{k}} \cdot a_{22} & \textcolor{white}{\colorbox{magenta}{k}} \cdot a_{23} \\
\textcolor{white}{\colorbox{magenta}{k}} \cdot a_{31} & \textcolor{white}{\colorbox{magenta}{k}} \cdot a_{32} & \textcolor{white}{\colorbox{magenta}{k}} \cdot a_{33}
\end{bmatrix}
$$