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Does the following system have a unique solution? Why?

[tex]\[
\begin{cases}
6x - 8y = 5 \\
-3x + 4y = -4
\end{cases}
\][/tex]

A. Yes, because the determinant of the coefficient matrix is 0.
B. No, because the determinant of the coefficient matrix is 24.
C. No, because the determinant of the coefficient matrix is 0.
D. Yes, because the determinant of the coefficient matrix is 24.

Sagot :

To determine whether the given system of equations has a unique solution, we need to examine the determinant of the coefficient matrix. Let's break down the steps:

1. Write down the system of equations:
[tex]\[ \begin{cases} 6x - 8y = 5 \\ -3x + 4y = -4 \end{cases} \][/tex]

2. Form the coefficient matrix:
The coefficients of the variables [tex]\(x\)[/tex] and [tex]\(y\)[/tex] in the equations form the matrix:
[tex]\[ \begin{bmatrix} 6 & -8 \\ -3 & 4 \end{bmatrix} \][/tex]

3. Calculate the determinant of the coefficient matrix:
To find the determinant of the matrix
[tex]\[ \begin{bmatrix} 6 & -8 \\ -3 & 4 \end{bmatrix} \][/tex]
we use the formula for the determinant of a 2x2 matrix:
[tex]\[ \text{det}(A) = ad - bc \][/tex]
where [tex]\(a = 6\)[/tex], [tex]\(b = -8\)[/tex], [tex]\(c = -3\)[/tex], and [tex]\(d = 4\)[/tex]. Now substitute these values into the formula:
[tex]\[ \text{det}(A) = (6 \cdot 4) - (-8 \cdot -3) = 24 - 24 = 0 \][/tex]

4. Interpret the determinant:
The determinant of the coefficient matrix is [tex]\(0\)[/tex].

5. Conclusion about the solution:
If the determinant of the coefficient matrix is [tex]\(0\)[/tex], it means that the system of equations does not have a unique solution. In this case, the system could either have no solution or infinitely many solutions, but it does not have exactly one unique solution.

Thus, the correct answer is:
```
No, because the determinant of the coefficient matrix is 0.
```