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Solve the system of equations using elimination:

[tex]\[
\begin{cases}
3x + 2y = -1 \\
x - 2y = 11
\end{cases}
\][/tex]

Choose the correct solution:

A. [tex]\(\left(\frac{5}{2}, -\frac{17}{4}\right)\)[/tex]
B. [tex]\((-5, 8)\)[/tex]
C. [tex]\(\left(4, -\frac{7}{2}\right)\)[/tex]
D. [tex]\((3, -4)\)[/tex]

Sagot :

Certainly! Let's solve the system of equations using the elimination method:

[tex]\[ \begin{cases} 3x + 2y = -1 \\ x - 2y = 11 \end{cases} \][/tex]

### Step 1: Align the Coefficients of [tex]\(y\)[/tex]

First, we want to align the coefficients of [tex]\(y\)[/tex] in both equations so that they can be eliminated.

Starting with the second equation [tex]\(x - 2y = 11\)[/tex], we can multiply it by 1:

[tex]\[ 1 \cdot (x - 2y) = 1 \cdot 11 \\ x - 2y = 11 \][/tex]

The first equation remains:

[tex]\[ 3x + 2y = -1 \][/tex]

### Step 2: Add the Equations to Eliminate [tex]\(y\)[/tex]

Now we add the two equations together to eliminate [tex]\(y\)[/tex]:

[tex]\[ (3x + 2y) + (x - 2y) = -1 + 11 \][/tex]
[tex]\[ 3x + 2y + x - 2y = 10 \][/tex]
[tex]\[ 4x = 10 \][/tex]
[tex]\[ x = \frac{10}{4} \][/tex]
[tex]\[ x = \frac{5}{2} \][/tex]

### Step 3: Substitute [tex]\(x\)[/tex] Back to Find [tex]\(y\)[/tex]

Next, we substitute the value of [tex]\(x\)[/tex] back into one of the original equations to find [tex]\(y\)[/tex]. We'll use the second equation:

[tex]\[ x - 2y = 11 \][/tex]
[tex]\[ \frac{5}{2} - 2y = 11 \][/tex]

Subtract [tex]\(\frac{5}{2}\)[/tex] from both sides:

[tex]\[ -2y = 11 - \frac{5}{2} \][/tex]
[tex]\[ -2y = \frac{22}{2} - \frac{5}{2} \][/tex]
[tex]\[ -2y = \frac{17}{2} \][/tex]

Divide both sides by [tex]\(-2\)[/tex]:

[tex]\[ y = -\frac{17}{4} \][/tex]

### Conclusion

Therefore, the solution to the system is:

[tex]\[ \left( x, y \right) = \left( \frac{5}{2}, -\frac{17}{4} \right) \][/tex]

So the correct answer from the given options is:

[tex]\[ \left( \frac{5}{2}, -\frac{17}{4} \right) \][/tex]