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Write the augmented matrix of the system and use the matrix method to solve the system. \( \begin{array}{l}-x+4 y+3 z=-16 \\ 3 x+y+z=10 \\ x+y+z=0\end{array} \) Select the correct choice and, if necessary, fill in the answer boxes to complete your choice. A. This system has exactly one solution. The solution is ( (Type integers or decimals.) B. This system has infinitely many solutions of the form ( \( \square, \square, z) \), where \( z \) is any real number. (Type integers or decimals.) C. This system has no solution.

Ask by Fowler Rose. in the United States
Feb 21,2025

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Tutor-Verified Answer

Answer

The system has exactly one solution: \( x = 5 \), \( y = 4 \), \( z = -9 \).

Solution

To solve the given system of equations using the matrix method, we first need to write the augmented matrix for the system: The system of equations is: 1. \(-x + 4y + 3z = -16\) 2. \(3x + y + z = 10\) 3. \(x + y + z = 0\) The augmented matrix for this system can be represented as follows: \[ \begin{bmatrix} -1 & 4 & 3 & | & -16 \\ 3 & 1 & 1 & | & 10 \\ 1 & 1 & 1 & | & 0 \end{bmatrix} \] Next, we will use row operations to reduce this augmented matrix to row echelon form or reduced row echelon form. ### Step 1: Row Operations 1. **Swap Row 1 and Row 3** to make the leading coefficient of the first row positive: \[ \begin{bmatrix} 1 & 1 & 1 & | & 0 \\ 3 & 1 & 1 & | & 10 \\ -1 & 4 & 3 & | & -16 \end{bmatrix} \] 2. **Eliminate the first column below Row 1**: - Row 2: \(R_2 - 3R_1\) - Row 3: \(R_3 + R_1\) Performing these operations gives: \[ \begin{bmatrix} 1 & 1 & 1 & | & 0 \\ 0 & -2 & -2 & | & 10 \\ 0 & 5 & 4 & | & -16 \end{bmatrix} \] 3. **Simplify Row 2** by dividing by -2: \[ \begin{bmatrix} 1 & 1 & 1 & | & 0 \\ 0 & 1 & 1 & | & -5 \\ 0 & 5 & 4 & | & -16 \end{bmatrix} \] 4. **Eliminate the second column below Row 2**: - Row 3: \(R_3 - 5R_2\) Performing this operation gives: \[ \begin{bmatrix} 1 & 1 & 1 & | & 0 \\ 0 & 1 & 1 & | & -5 \\ 0 & 0 & -1 & | & 9 \end{bmatrix} \] 5. **Simplify Row 3** by multiplying by -1: \[ \begin{bmatrix} 1 & 1 & 1 & | & 0 \\ 0 & 1 & 1 & | & -5 \\ 0 & 0 & 1 & | & -9 \end{bmatrix} \] ### Step 2: Back Substitution Now we can back substitute to find the values of \(x\), \(y\), and \(z\): From Row 3: \[ z = -9 \] From Row 2: \[ y + z = -5 \implies y - 9 = -5 \implies y = 4 \] From Row 1: \[ x + y + z = 0 \implies x + 4 - 9 = 0 \implies x = 5 \] ### Final Solution The solution to the system is: \[ (x, y, z) = (5, 4, -9) \] ### Conclusion Since we found a unique solution, the correct choice is: **A. This system has exactly one solution. The solution is (5, 4, -9).**

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The Deep Dive

To start, the augmented matrix for the given system of equations is: \[ \begin{pmatrix} -1 & 4 & 3 & | & -16 \\ 3 & 1 & 1 & | & 10 \\ 1 & 1 & 1 & | & 0 \end{pmatrix} \] Now, using the matrix method (specifically, row reduction), we can solve this matrix. The goal is to apply Gaussian elimination to bring the matrix to row-echelon form. 1. Start by swapping the first row with the third row to get a leading 1: \[ \begin{pmatrix} 1 & 1 & 1 & | & 0 \\ 3 & 1 & 1 & | & 10 \\ -1 & 4 & 3 & | & -16 \end{pmatrix} \] 2. Now, eliminate the x terms in the second and third rows. For the second row, we perform the operation \( R_2 - 3R_1 \): \[ \begin{pmatrix} 1 & 1 & 1 & | & 0 \\ 0 & -2 & -2 & | & 10 \\ -1 & 4 & 3 & | & -16 \end{pmatrix} \] For the third row, we perform \( R_3 + R_1 \): \[ \begin{pmatrix} 1 & 1 & 1 & | & 0 \\ 0 & -2 & -2 & | & 10 \\ 0 & 5 & 4 & | & -16 \end{pmatrix} \] 3. Next, we can simplify the second row by multiplying it by \(-\frac{1}{2}\): \[ \begin{pmatrix} 1 & 1 & 1 & | & 0 \\ 0 & 1 & 1 & | & -5 \\ 0 & 5 & 4 & | & -16 \end{pmatrix} \] 4. Now eliminate \( y \) from the third row by performing \( R_3 - 5R_2 \): \[ \begin{pmatrix} 1 & 1 & 1 & | & 0 \\ 0 & 1 & 1 & | & -5 \\ 0 & 0 & -1 & | & 9 \end{pmatrix} \] 5. Finally, multiply the third row by \(-1\): \[ \begin{pmatrix} 1 & 1 & 1 & | & 0 \\ 0 & 1 & 1 & | & -5 \\ 0 & 0 & 1 & | & -9 \end{pmatrix} \] Now back substitute to find the values: From Row 3: \( z = -9 \) From Row 2: \( y + z = -5 \) → \( y - 9 = -5 \) → \( y = 4 \) From Row 1: \( x + y + z = 0 \) → \( x + 4 - 9 = 0 \) → \( x = 5 \) Thus, the solution to the system is \( (5, 4, -9) \). The correct choice is A. This system has exactly one solution. The solution is (5, 4, -9).

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