Answered

Select the correct answer.

[tex]\[
A = 2 \left[ \begin{array}{ccc}
-6 & 7 & -4 \\
4 & -4 & 3 \\
-2 & 4 & 0 \\
7 & 0 & -2
\end{array} \right],
B = -3 \left[ \begin{array}{ccc}
5 & -9 & 1 \\
3 & 6 & -3 \\
8 & 9 & 1 \\
4 & 9 & -9
\end{array} \right]
\][/tex]

In [tex]\( C = A + B \)[/tex], what is the value of the entry represented by [tex]\( c_{41} \)[/tex]?

A. -2
B. 2
C. -16
D. 16



Answer :

To find the value of [tex]\(c_{41}\)[/tex] in the matrix [tex]\(C = A + B\)[/tex], we need to follow these steps:

1. Construct Matrix [tex]\(A\)[/tex] and Matrix [tex]\(B\)[/tex]:
- Given:
[tex]\[ A = 2 \left[\begin{array}{ccc} -6 & 7 & -4 \\ 4 & -4 & 3 \\ -2 & 4 & 0 \\ 7 & 0 & -2 \end{array}\right] \][/tex]
[tex]\[ B = -3 \left[\begin{array}{ccc} 5 & -9 & 1 \\ 3 & 6 & -3 \\ 8 & 9 & 1 \\ 4 & 9 & -9 \end{array}\right] \][/tex]

2. Calculate Matrix [tex]\(A\)[/tex]:
- Multiply each element in the matrix by 2:
[tex]\[ A = \left[\begin{array}{ccc} 2 \cdot (-6) & 2 \cdot 7 & 2 \cdot (-4) \\ 2 \cdot 4 & 2 \cdot (-4) & 2 \cdot 3 \\ 2 \cdot (-2) & 2 \cdot 4 & 2 \cdot 0 \\ 2 \cdot 7 & 2 \cdot 0 & 2 \cdot (-2) \end{array}\right] = \left[\begin{array}{ccc} -12 & 14 & -8 \\ 8 & -8 & 6 \\ -4 & 8 & 0 \\ 14 & 0 & -4 \end{array}\right] \][/tex]

3. Calculate Matrix [tex]\(B\)[/tex]:
- Multiply each element in the matrix by -3:
[tex]\[ B = \left[\begin{array}{ccc} -3 \cdot 5 & -3 \cdot (-9) & -3 \cdot 1 \\ -3 \cdot 3 & -3 \cdot 6 & -3 \cdot (-3) \\ -3 \cdot 8 & -3 \cdot 9 & -3 \cdot 1 \\ -3 \cdot 4 & -3 \cdot 9 & -3 \cdot (-9) \end{array}\right] = \left[\begin{array}{ccc} -15 & 27 & -3 \\ -9 & -18 & 9 \\ -24 & -27 & -3 \\ -12 & -27 & 27 \end{array}\right] \][/tex]

4. Compute Matrix [tex]\(C = A + B\)[/tex]:
- Add the corresponding elements of matrices [tex]\(A\)[/tex] and [tex]\(B\)[/tex]:
[tex]\[ C = \left[\begin{array}{ccc} -12 & 14 & -8 \\ 8 & -8 & 6 \\ -4 & 8 & 0 \\ 14 & 0 & -4 \end{array}\right] + \left[\begin{array}{ccc} -15 & 27 & -3 \\ -9 & -18 & 9 \\ -24 & -27 & -3 \\ -12 & -27 & 27 \end{array}\right] \][/tex]
This results in:
[tex]\[ C = \left[\begin{array}{ccc} -12 + (-15) & 14 + 27 & -8 + (-3) \\ 8 + (-9) & -8 + (-18) & 6 + 9 \\ -4 + (-24) & 8 + (-27) & 0 + (-3) \\ 14 + (-12) & 0 + (-27) & -4 + 27 \end{array}\right] \][/tex]
[tex]\[ C = \left[\begin{array}{ccc} -27 & 41 & -11 \\ -1 & -26 & 15 \\ -28 & -19 & -3 \\ 2 & -27 & 23 \end{array}\right] \][/tex]

5. Extract the Value of [tex]\(c_{41}\)[/tex]:
- The entry [tex]\(c_{41}\)[/tex] corresponds to the element in the 4th row and 1st column of matrix [tex]\(C\)[/tex], which is [tex]\(2\)[/tex].

Therefore, the correct answer is [tex]\( \boxed{2} \)[/tex].