Write each equation in standard form:
3x + y + 3z = 11
x + 2y + z = 7
-x + y + z = 0
In matrix form, this is
[tex]\begin{bmatrix}3&1&3\\1&2&1\\-1&1&1\end{bmatrix}\begin{bmatrix}x\\y\\z\end{bmatrix}=\begin{bmatrix}11\\7\\0\end{bmatrix}[/tex]
and in augmented matrix form,
[tex]\left[\begin{array}{ccc|c}3&1&3&11\\1&2&1&7\\-1&1&1&0\end{bmatrix}\right][/tex]
Now for the row operations:
• Add row 1 to -3 (row 2), and add row 1 to 3 (row 3):
[tex]\left[\begin{array}{ccc|c}3&1&3&11\\0&-5&0&-10\\0&4&6&11\end{bmatrix}\right][/tex]
• Multiply row 2 by -1/5:
[tex]\left[\begin{array}{ccc|c}3&1&3&11\\0&1&0&2\\0&4&6&11\end{bmatrix}\right][/tex]
• Add -4 (row 2) to row 3:
[tex]\left[\begin{array}{ccc|c}3&1&3&11\\0&1&0&2\\0&0&6&3\end{bmatrix}\right][/tex]
• Multiply row 3 by 1/6:
[tex]\left[\begin{array}{ccc|c}3&1&3&11\\0&1&0&2\\0&0&1&\frac12\end{bmatrix}\right][/tex]
• Add -1 (row 2) and -3 (row 3) to row 1:
[tex]\left[\begin{array}{ccc|c}3&0&0&\frac{15}2\\0&1&0&2\\0&0&1&\frac12\end{bmatrix}\right][/tex]
• Mutiply row 1 by 1/3:
[tex]\left[\begin{array}{ccc|c}1&0&0&\frac52\\0&1&0&2\\0&0&1&\frac12\end{bmatrix}\right][/tex]
Then the solution to the system is (x, y, z) = (5/2, 2, 1/2).
