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2 câu trả lời 190
`{(2x+y-3z=3),(x+y+3z=2),(3x-2y+z=-1):}`
`<=> {(x-6z=1),(x+y+3z=2),(3x-2y+z=-1):}`
`<=> {(x-6z=1),(2x+2y+6z=4),(3x-2y+z=-1):}`
`<=> {(x-6z=1),(5x+7z=3),(3x-2y+z=-1):}`
`<=> {(5x-30z=5),(5x+7z=3),(3x-2y+z=-1):}`
`<=> {(-37z=2),(5x+7z=3),(3x-2y+z=-1):}`
`<=> {(z=-2/37),(5x-14/37=3),(3x-2y+z=-1):}`
`<=> {(z=-2/37),(5x=125/37),(3x-2y+z=-1):}`
`<=> {(z=-2/37),(x=25/37),(75/37-2y-2/37=-1):}`
`<=> {(z=-2/37),(x=25/37),(y=55/37):}`
`->` Nghiệm `(25/37; 55/37;-2/37)`
To solve the system of equations:
1. \( 2x + y - 3z = 3 \) \quad (Equation 1)
2. \( x + y + 3z = 2 \) \quad (Equation 2)
3. \( 3x - 2y + z = -1 \) \quad (Equation 3)
Let's use the method of elimination or substitution. We'll start by manipulating the equations to eliminate variables.
### Step 1: Solve for one variable
Let’s solve Equation 2 for \( y \):
\[
y = 2 - x - 3z \quad \text{(Equation 4)}
\]
### Step 2: Substitute into other equations
Now, substitute Equation 4 into Equations 1 and 3:
**Substituting into Equation 1:**
\[
2x + (2 - x - 3z) - 3z = 3
\]
Simplifying:
\[
2x + 2 - x - 3z - 3z = 3
\]
\[
x - 6z + 2 = 3
\]
\[
x - 6z = 1 \quad \text{(Equation 5)}
\]
**Substituting into Equation 3:**
\[
3x - 2(2 - x - 3z) + z = -1
\]
Simplifying:
\[
3x - 4 + 2x + 6z + z = -1
\]
\[
5x + 7z - 4 = -1
\]
\[
5x + 7z = 3 \quad \text{(Equation 6)}
\]
### Step 3: Solve the new system of equations
Now we have a new system of equations to solve:
1. \( x - 6z = 1 \) \quad (Equation 5)
2. \( 5x + 7z = 3 \) \quad (Equation 6)
From Equation 5, we can express \( x \) in terms of \( z \):
\[
x = 1 + 6z \quad \text{(Equation 7)}
\]
### Step 4: Substitute into Equation 6
Substitute Equation 7 into Equation 6:
\[
5(1 + 6z) + 7z = 3
\]
Expanding:
\[
5 + 30z + 7z = 3
\]
\[
30z + 7z = 3 - 5
\]
\[
37z = -2
\]
\[
z = -\frac{2}{37}
\]
### Step 5: Back substitute to find \( x \) and \( y \)
Now substitute \( z \) back into Equation 7 to find \( x \):
\[
x = 1 + 6\left(-\frac{2}{37}\right) = 1 - \frac{12}{37} = \frac{37}{37} - \frac{12}{37} = \frac{25}{37}
\]
Next, substitute \( z = -\frac{2}{37} \) into Equation 4 to find \( y \):
\[
y = 2 - \left(\frac{25}{37}\right) - 3\left(-\frac{2}{37}\right)
\]
\[
y = 2 - \frac{25}{37} + \frac{6}{37}
\]
\[
y = 2 - \frac{25 - 6}{37}
\]
\[
y = 2 - \frac{19}{37} = \frac{74}{37} - \frac{19}{37} = \frac{55}{37}
\]
### Final Solution
Thus, we find the solution:
\[
x = \frac{25}{37}, \quad y = \frac{55}{37}, \quad z = -\frac{2}{37}
\]
So the solution to the system of equations is:
\[
(x, y, z) = \left(\frac{25}{37}, \frac{55}{37}, -\frac{2}{37}\right)
\]
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