Which of the following matrices can NOT be obtained from the matrix pmatrix-1&21&-1pmatrix…

Question

Which of the following matrices can NOT be obtained from the matrix $\begin{pmatrix}-1&2\1&-1\end{pmatrix}$ by a single elementary row operation?

Accepted Answer

- (A): $R_1	o R_1+R_2$ gives $\begin{pmatrix}0&1\1&-1\end{pmatrix}$ --- possible.
- (B): $R_1\leftrightarrow R_2$ gives $\begin{pmatrix}1&-1\-1&2\end{pmatrix}$ --- possible.
- (D): $R_2	o R_2+2R_1$ gives $\begin{pmatrix}-1&2\-1&3\end{pmatrix}$ --- possible.
- (C): no single elementary row operation on the original matrix produces $\begin{pmatrix}-1&2\-2&7\end{pmatrix}$ --- not possible.

Solutions · 1