1. What is the solution to the system of equations?

[tex]
\left\{\begin{array}{r}
-3x - y + z = 6 \\
-3x - y + 3z = 0 \\
x - 3z = 3
\end{array}\right.
[/tex]



Answer :

To find the solution to the system of equations:
[tex]\[ \left\{\begin{array}{rcl} -3x - y + z & = & 6 \quad \text{(1)} \\ -3x - y + 3z & = & 0 \quad \text{(2)} \\ x - 3z & = & 3 \quad \text{(3)} \end{array}\right. \][/tex]

We'll solve the system of equations step-by-step:

1. Start with equation (3) to solve for [tex]\(x\)[/tex] in terms of [tex]\(z\)[/tex]:
[tex]\[ x - 3z = 3 \quad \Rightarrow \quad x = 3 + 3z \quad \text{(4)} \][/tex]

2. Substitute [tex]\(x = 3 + 3z\)[/tex] into equations (1) and (2):
- For equation (1):
[tex]\[ -3(3 + 3z) - y + z = 6 \\ -9 - 9z - y + z = 6 \\ -9 - 8z - y = 6 \\ -8z - y = 15 \\ y = -8z - 15 \quad \text{(5)} \][/tex]

- For equation (2):
[tex]\[ -3(3 + 3z) - y + 3z = 0 \\ -9 - 9z - y + 3z = 0 \\ -9 - 6z - y = 0 \\ y = -6z - 9 \quad \text{(6)} \][/tex]

3. Set equations (5) and (6) equal to each other, since they both equal [tex]\(y\)[/tex]:
[tex]\[ -8z - 15 = -6z - 9 \\ -8z + 6z = -9 + 15 \\ -2z = 6 \\ z = -3 \][/tex]

4. Substitute [tex]\(z = -3\)[/tex] back into equations (4) and (5):
- For [tex]\(x\)[/tex]:
[tex]\[ x = 3 + 3(-3) \\ x = 3 - 9 \\ x = -6 \][/tex]

- For [tex]\(y\)[/tex]:
[tex]\[ y = -8(-3) - 15 \\ y = 24 - 15 \\ y = 9 \][/tex]

Thus, the solution to the system of equations is:
[tex]\[ \boxed{x = -6, y = 9, z = -3} \][/tex]