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Which of the following is the result of the operation below?

[tex]\[
\left[\begin{array}{ccc|c}1 & 2 & 3 & 6 \\ 1 & 1 & 1 & -2 \\ 0 & 2 & 1 & 5\end{array}\right] \xrightarrow{-R_1+R_2 \rightarrow R_2}
\][/tex]

A. [tex]\[
\left[\begin{array}{ccc|c}1 & 2 & 3 & 6 \\ 0 & -1 & -2 & -8 \\ 0 & 2 & 1 & 5\end{array}\right]
\][/tex]

B. [tex]\[
\left[\begin{array}{ccc|c}1 & 2 & 3 & 6 \\ 0 & 1 & 2 & 8 \\ 0 & 2 & 1 & 5\end{array}\right]
\][/tex]


Sagot :

To solve this, we will perform the operation [tex]\(-R1 + R2 \rightarrow R2\)[/tex] and determine the resulting matrix.

Let's start with the initial matrix:
[tex]\[ \left[\begin{array}{ccc|c} 1 & 2 & 3 & 6 \\ 1 & 1 & 1 & -2 \\ 0 & 2 & 1 & 5 \end{array}\right] \][/tex]

We need to apply the operation [tex]\(-R1 + R2 \rightarrow R2\)[/tex]. This means we will subtract the elements of row 1 from the corresponding elements of row 2 to get the new row 2.

Step-by-step, it looks like this:

1. Element in column 1 of R2:
[tex]\[ 1 - 1 = 0 \][/tex]

2. Element in column 2 of R2:
[tex]\[ 1 - 2 = -1 \][/tex]

3. Element in column 3 of R2:
[tex]\[ 1 - 3 = -2 \][/tex]

4. Element in the augmented column of R2:
[tex]\[ -2 - 6 = -8 \][/tex]

The updated matrix is then:
[tex]\[ \left[\begin{array}{ccc|c} 1 & 2 & 3 & 6 \\ 0 & -1 & -2 & -8 \\ 0 & 2 & 1 & 5 \end{array}\right] \][/tex]

Therefore, the result of the operation [tex]\(-R1 + R2 \rightarrow R2\)[/tex] applied to the given matrix is:
[tex]\[ \left[\begin{array}{ccc|c} 1 & 2 & 3 & 6 \\ 0 & -1 & -2 & -8 \\ 0 & 2 & 1 & 5 \end{array}\right] \][/tex]

Among the given options, the correct resulting matrix is:
[tex]\[ \left[\begin{array}{ccc|c} 1 & 2 & 3 & 6 \\ 0 & -1 & -2 & -8 \\ 0 & 2 & 1 & 5 \end{array}\right] \][/tex]

So, the correct option is:
[tex]\[ \left[\begin{array}{ccc|c} 1 & 2 & 3 & 6 \\ 0 & -1 & -2 & -8 \\ 0 & 2 & 1 & 5 \end{array}\right] \][/tex]