QuestionAugust 27, 2025

Use Cramer's Rule to find y in the system of equations below. 2x-3y=17 5x+4y=8 Answer: square

Use Cramer's Rule to find y in the system of equations below. 2x-3y=17 5x+4y=8 Answer: square
Use Cramer's Rule to find y in the system of equations below.
2x-3y=17
5x+4y=8
Answer: square

Solution
4.2(320 votes)

Answer

y = -3 Explanation 1. Write the system in matrix form The system can be written as AX = B, where A = \begin{bmatrix} 2 & -3 \\ 5 & 4 \end{bmatrix}, X = \begin{bmatrix} x \\ y \end{bmatrix}, and B = \begin{bmatrix} 17 \\ 8 \end{bmatrix}. 2. Calculate the determinant of A \text{det}(A) = (2)(4) - (-3)(5) = 8 + 15 = 23. 3. Form the matrix A_y by replacing the second column of A with B A_y = \begin{bmatrix} 2 & 17 \\ 5 & 8 \end{bmatrix}. 4. Calculate the determinant of A_y \text{det}(A_y) = (2)(8) - (17)(5) = 16 - 85 = -69. 5. Apply Cramer's Rule to find y **Cramer's Rule**: y = \frac{\text{det}(A_y)}{\text{det}(A)} = \frac{-69}{23} = -3.

Explanation

1. Write the system in matrix form<br /> The system can be written as $AX = B$, where $A = \begin{bmatrix} 2 & -3 \\ 5 & 4 \end{bmatrix}$, $X = \begin{bmatrix} x \\ y \end{bmatrix}$, and $B = \begin{bmatrix} 17 \\ 8 \end{bmatrix}$.<br /><br />2. Calculate the determinant of A<br /> $\text{det}(A) = (2)(4) - (-3)(5) = 8 + 15 = 23$.<br /><br />3. Form the matrix $A_y$ by replacing the second column of $A$ with $B$<br /> $A_y = \begin{bmatrix} 2 & 17 \\ 5 & 8 \end{bmatrix}$.<br /><br />4. Calculate the determinant of $A_y$<br /> $\text{det}(A_y) = (2)(8) - (17)(5) = 16 - 85 = -69$.<br /><br />5. Apply Cramer's Rule to find y<br /> **Cramer's Rule**: $y = \frac{\text{det}(A_y)}{\text{det}(A)} = \frac{-69}{23} = -3$.
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