向量组的线性相关性与秩（C019）

问题

若 $\boldsymbol{\beta}_{1}$, $\boldsymbol{\beta}_{2}$, $\cdots$, $\boldsymbol{\beta}_{t}$ 可由 $\boldsymbol{\alpha}_{1}$, $\boldsymbol{\alpha}_{2}$, $\cdots$, $\boldsymbol{\alpha}_{s}$, 线性表出，则 $\mathrm{r}\left(\boldsymbol{\beta}_{1}, \boldsymbol{\beta}_{2}, \cdots, \boldsymbol{\beta}_{\mathrm{t}}\right)$ 与 $\mathrm{r}\left(\boldsymbol{\alpha}_{1}, \boldsymbol{\alpha}_{2}, \cdots, \boldsymbol{\alpha}_{\mathrm{s}}\right)$ 之间具有怎样的关系？

选项

[A].   $\mathrm{r}\left(\boldsymbol{\beta}_{1}, \boldsymbol{\beta}_{2}, \cdots, \boldsymbol{\beta}_{\mathrm{t}}\right)$ $<$ $\mathrm{r}\left(\boldsymbol{\alpha}_{1}, \boldsymbol{\alpha}_{2}, \cdots, \boldsymbol{\alpha}_{\mathrm{s}}\right)$

[B].   $\mathrm{r}\left(\boldsymbol{\beta}_{1}, \boldsymbol{\beta}_{2}, \cdots, \boldsymbol{\beta}_{\mathrm{t}}\right)$ $\geqslant$ $\mathrm{r}\left(\boldsymbol{\alpha}_{1}, \boldsymbol{\alpha}_{2}, \cdots, \boldsymbol{\alpha}_{\mathrm{s}}\right)$

[C].   $\mathrm{r}\left(\boldsymbol{\beta}_{1}, \boldsymbol{\beta}_{2}, \cdots, \boldsymbol{\beta}_{\mathrm{t}}\right)$ $\leqslant$ $\mathrm{r}\left(\boldsymbol{\alpha}_{1}, \boldsymbol{\alpha}_{2}, \cdots, \boldsymbol{\alpha}_{\mathrm{s}}\right)$

[D].   $\mathrm{r}\left(\boldsymbol{\beta}_{1}, \boldsymbol{\beta}_{2}, \cdots, \boldsymbol{\beta}_{\mathrm{t}}\right)$ $=$ $\mathrm{r}\left(\boldsymbol{\alpha}_{1}, \boldsymbol{\alpha}_{2}, \cdots, \boldsymbol{\alpha}_{\mathrm{s}}\right)$

答 案

$\mathrm{r}\left(\boldsymbol{\beta}_{1}, \boldsymbol{\beta}_{2}, \cdots, \boldsymbol{\beta}_{\mathrm{t}}\right)$ $\leqslant$ $\mathrm{r}\left(\boldsymbol{\alpha}_{1}, \boldsymbol{\alpha}_{2}, \cdots, \boldsymbol{\alpha}_{\mathrm{s}}\right)$