Given
[tex]\[
\left[\begin{array}{cc}12 & -13 \\ 17 & -22\end{array}\right]\left[\begin{array}{l}x \\ y\end{array}\right]=\left[\begin{array}{c}7 \\ -51\end{array}\right],
\][/tex]
what is [tex]\(\left|A_y\right|\)[/tex] ?

A. [tex]\(\left|\begin{array}{cc}7 & -13 \\ -51 & -22\end{array}\right|\)[/tex]

B. [tex]\(\left|\begin{array}{cc}12 & 7 \\ 17 & -51\end{array}\right|\)[/tex]

C. [tex]\(\left|\begin{array}{cc}7 & -51 \\ 17 & -22\end{array}\right|\)[/tex]

D. [tex]\(\left|\begin{array}{cc}12 & -13 \\ 7 & -51\end{array}\right|\)[/tex]



Answer :

To find [tex]\(\left|A_y\right|\)[/tex] in the context of the given matrix equation and options, we need to understand that [tex]\(\left|A_y\right|\)[/tex] represents the determinant of the matrix formed by replacing the second column of the coefficient matrix [tex]\(A\)[/tex] with the constants from the right-hand side of the equation.

The system of equations given is:

[tex]\[ \begin{cases} 12x - 13y = 7 \\ 17x - 22y = -51 \end{cases} \][/tex]

The coefficient matrix [tex]\(A\)[/tex] is:

[tex]\[ A = \begin{pmatrix} 12 & -13 \\ 17 & -22 \end{pmatrix} \][/tex]

The constants matrix is:

[tex]\[ \mathbf{b} = \begin{pmatrix} 7 \\ -51 \end{pmatrix} \][/tex]

To find [tex]\(\left|A_y\right|\)[/tex], we replace the second column of [tex]\(A\)[/tex] with [tex]\(\mathbf{b}\)[/tex]:

1. Start with possible replacements from the given options to construct the matrices.

[tex]\(\begin{pmatrix} 7 & -13 \\ -51 & -22 \end{pmatrix}\)[/tex]

2. Calculate the determinant:

[tex]\[ \left| \begin{pmatrix} 7 & -13 \\ -51 & -22 \end{pmatrix} \right| = (7 \cdot -22) - (-13 \cdot -51) = -154 - 663 = -817 \][/tex]

Following this result, let's analyze the determinants from the remaining options:

[tex]\[ \left| \begin{pmatrix} 12 & 7 \\ 17 & -51 \end{pmatrix} \right| = (12 \cdot -51) - (7 \cdot 17) = -612 - 119 = -731 \][/tex]

[tex]\[ \left| \begin{pmatrix} 7 & -51 \\ 17 & -22 \end{pmatrix} \right| = (7 \cdot -22) - (-51 \cdot 17) = -154 + 867 = 713 \][/tex]

[tex]\[ \left| \begin{pmatrix} 12 & -13 \\ 7 & -51 \end{pmatrix} \right| = (12 \cdot -51) - (-13 \cdot 7) = -612 + 91 = -521 \][/tex]

From these calculations, the correct determinant matching [tex]\(\left|A_y\right|\)[/tex] is the one from:
[tex]\[ \left| \begin{pmatrix} 7 & -51 \\ 17 & -22 \end{pmatrix} \right| = 713 \][/tex]

So, [tex]\(\left|A_y\right|\)[/tex] is:
[tex]\[ 713 \][/tex]