To solve the given system of linear equations using Gaussian elimination with back-substitution, we will follow these steps:
1. Write the augmented matrix for the system of equations:
[tex]\[
\begin{aligned}
3x - 2y + z &= 11 \\
-x + y + 2z &= -11 \\
x - y - 4z &= 17
\end{aligned}
\][/tex]
The augmented matrix representing this system is:
[tex]\[
\left[\begin{array}{ccc|c}
3 & -2 & 1 & 11 \\
-1 & 1 & 2 & -11 \\
1 & -1 & -4 & 17
\end{array}\right]
\][/tex]
2. Perform Gaussian elimination to transform the matrix into an upper triangular form.
- Normalize the first row by dividing by the pivot element (3):
[tex]\[
\left[\begin{array}{ccc|c}
1 & -0.6667 & 0.3333 & 3.6667 \\
-1 & 1 & 2 & -11 \\
1 & -1 & -4 & 17
\end{array}\right]
\][/tex]
- Eliminate the entries below the pivot in column 1:
[tex]\[
\left[\begin{array}{ccc|c}
1 & -0.6667 & 0.3333 & 3.6667 \\
0 & 0.3333 & 2.3333 & -7.3333 \\
0 & -0.3333 & -4.3333 & 13.3333
\end{array}\right]
\][/tex]
- Normalize the second row by dividing by the pivot element (0.3333):
[tex]\[
\left[\begin{array}{ccc|c}
1 & -0.6667 & 0.3333 & 3.6667 \\
0 & 1 & 7 & -22 \\
0 & -0.3333 & -4.3333 & 13.3333
\end{array}\right]
\][/tex]
- Eliminate the entries below the pivot in column 2:
[tex]\[
\left[\begin{array}{ccc|c}
1 & -0.6667 & 0.3333 & 3.6667 \\
0 & 1 & 7 & -22 \\
0 & 0 & -2 & 6
\end{array}\right]
\][/tex]
- Normalize the third row by dividing by the pivot element (-2):
[tex]\[
\left[\begin{array}{ccc|c}
1 & -0.6667 & 0.3333 & 3.6667 \\
0 & 1 & 7 & -22 \\
0 & 0 & 1 & -3
\end{array}\right]
\][/tex]
3. Perform back-substitution to find the values of [tex]\(x, y,\)[/tex] and [tex]\(z\)[/tex].
- From the third row:
[tex]\[
z = -3
\][/tex]
- Substitute [tex]\(z = -3\)[/tex] into the second row equation:
[tex]\[
y + 7(-3) = -22 \implies y - 21 = -22 \implies y = -1
\][/tex]
- Substitute [tex]\( y = -1 \)[/tex] and [tex]\( z = -3 \)[/tex] into the first row equation:
[tex]\[
x - 0.6667(-1) + 0.3333(-3) = 3.6667 \implies x + 0.6667 - 1 = 3.6667 \implies x + 0.6667 = 4.6667 \implies x = 4
\][/tex]
So, the solution to the system of equations is:
[tex]\[
(x, y, z) = (4, -1, -3)
\][/tex]
