Use the Gauss-Jordan method to solve the given system of equations. \[ \begin{aligned} x+2 y+z & =8 \\ 2 x+y-5 z & =1 \\ 3 x+y+2 z & =-1 \end{aligned} \] What is the reduced row echelon form of the augmented matrix? (Simplify your answers.) \( \square \) \( \square \) \( \square \) \( \square \) \( \square \)
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The Deep Dive
To solve the given system of equations using the Gauss-Jordan method, we start by writing the augmented matrix: \[ \begin{bmatrix} 1 & 2 & 1 & | & 8 \\ 2 & 1 & -5 & | & 1 \\ 3 & 1 & 2 & | & -1 \end{bmatrix} \] Next, we perform row operations to achieve reduced row echelon form (RREF). 1. **R1** is already fine: \( R_1 \rightarrow R_1 \). 2. Eliminate \( x \) from **R2** and **R3**: \[ R_2 \rightarrow R_2 - 2R_1 \Rightarrow [0, -3, -7 | -15] \] \[ R_3 \rightarrow R_3 - 3R_1 \Rightarrow [0, -5, -1 | -25] \] The matrix now looks like: \[ \begin{bmatrix} 1 & 2 & 1 & | & 8 \\ 0 & -3 & -7 & | & -15 \\ 0 & -5 & -1 & | & -25 \end{bmatrix} \] 3. Next, we simplify **R2** and **R3**: Divide **R2** by -3: \[ R_2 \rightarrow -\frac{1}{3} R_2 \Rightarrow [0, 1, \frac{7}{3} | 5] \] 4. Then, make R3 dependent on R2: \[ R_3 \rightarrow R_3 + 5R_2 \Rightarrow [0, 0, \frac{8}{3} | 0] \] The matrix is now: \[ \begin{bmatrix} 1 & 2 & 1 & | & 8 \\ 0 & 1 & \frac{7}{3} & | & 5 \\ 0 & 0 & 1 & | & 0 \end{bmatrix} \] 5. Finally, we back substitute to achieve the leading 1s in each pivot column: \[ R_1 \rightarrow R_1 - R_3 \quad R_2 \rightarrow R_2 - \frac{7}{3}R_3 \] After performing these steps, our augmented matrix simplifies to: \[ \begin{bmatrix} 1 & 0 & 0 & | & 1 \\ 0 & 1 & 0 & | & 5 \\ 0 & 0 & 1 & | & 0 \end{bmatrix} \] So, the reduced row echelon form of the augmented matrix is: \[ \begin{bmatrix} 1 & 0 & 0 & | & 1 \\ 0 & 1 & 0 & | & 5 \\ 0 & 0 & 1 & | & 0 \end{bmatrix} \] The final solutions for \( x, y, z \) are: \[ x = 1, \quad y = 5, \quad z = 0 \]
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