Answered

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Kamal wrote the augmented matrix below to represent a system of equations:

[tex]\[
\left[\begin{array}{ccc|c}
1 & 0 & 1 & -1 \\
1 & 3 & -1 & -9 \\
3 & 2 & 0 & -2
\end{array}\right]
\][/tex]

Which matrix results from the operation [tex]\(-3 R_2 \leftrightarrow R_2\)[/tex]?

A. [tex]\(\left[\begin{array}{ccc|c}
1 & 0 & 1 & -1 \\
-3 & -9 & 3 & 27 \\
3 & 2 & 0 & -2
\end{array}\right]\)[/tex]

B. [tex]\(\left[\begin{array}{ccc|c}
1 & 0 & 1 & -1 \\
-3 & -3 & -3 & -3 \\
3 & 2 & 0 & -2
\end{array}\right]\)[/tex]

Sagot :

To determine which matrix results from the given operation [tex]\(-3 R_2 \leftrightarrow R_2\)[/tex] on the original augmented matrix, we need to carefully apply the operation to the second row of the initial matrix.

Here is the original matrix:
[tex]\[ \left[\begin{array}{ccc|c} 1 & 0 & 1 & -1 \\ 1 & 3 & -1 & -9 \\ 3 & 2 & 0 & -2 \end{array}\right] \][/tex]

The operation [tex]\(-3 R_2 \leftrightarrow R_2\)[/tex] indicates that each element in the second row should be multiplied by [tex]\(-3\)[/tex].

Let's perform this operation on the second row step by step:

- For the first element of the second row: [tex]\(1 \times -3 = -3\)[/tex]
- For the second element of the second row: [tex]\(3 \times -3 = -9\)[/tex]
- For the third element of the second row: [tex]\(-1 \times -3 = 3\)[/tex]
- For the fourth element of the second row (the augmented part): [tex]\(-9 \times -3 = 27\)[/tex]

So the new second row after applying [tex]\(-3 R_2 \leftrightarrow R_2\)[/tex] will be:
[tex]\[ [-3, -9, 3, 27] \][/tex]

Thus, the resulting matrix will be:
[tex]\[ \left[\begin{array}{ccc|c} 1 & 0 & 1 & -1 \\ -3 & -9 & 3 & 27 \\ 3 & 2 & 0 & -2 \end{array}\right] \][/tex]

Therefore, the correct matrix resulting from the operation [tex]\(-3 R_2 \leftrightarrow R_2\)[/tex] is:
[tex]\[ \left[\begin{array}{ccc|c} 1 & 0 & 1 & -1 \\ -3 & -9 & 3 & 27 \\ 3 & 2 & 0 & -2 \end{array}\right] \][/tex]

This corresponds to the first given option:
[tex]\[ \left[\begin{array}{ccc|c} 1 & 0 & 1 & -1 \\ -3 & -9 & 3 & 27 \\ 3 & 2 & 0 & -2 \end{array}\right] \][/tex]