Find y, if \(\begin{pmatrix}5 & -6 \\2 & -7\end{pmatrix}\begin{pmatrix}x \\ y \end{pmatrix} = \begin{pmatrix}7 \\-11\end{pmatrix}\)
The correct answer is C. 3
To solve the matrix equation \(\begin{pmatrix}5 & -6 \\ 2 & -7\end{pmatrix} \begin{pmatrix}x \\ y\end{pmatrix} = \begin{pmatrix}7 \\ -11\end{pmatrix}\), we can perform matrix multiplication:
\(\begin{pmatrix}5 & -6 \\ 2 & -7\end{pmatrix} \begin{pmatrix}x \\ y\end{pmatrix} = \begin{pmatrix}5x - 6y \\ 2x - 7y\end{pmatrix}\)
Now we have the system of equations:
\(5x - 6y = 7\)
\(2x - 7y = -11\)
We can solve this system of equations to find the value of \(y\). Let's use the method of substitution:
From the first equation, we can isolate \(x\):
\(5x = 6y + 7\)
\(x = \frac{6y + 7}{5}\)
Now substitute this expression for \(x\) into the second equation:
\(2\left(\frac{6y + 7}{5}\right) - 7y = -11\)
Simplify the equation:
\(\frac{12y + 14}{5} - 7y = -11\)
Multiply both sides by 5 to eliminate the fraction:
12y + 14 - 35y = -55
Combine like terms:
-23y + 14 = -55
Subtract 14 from both sides:
-23y = -69
Divide by -23:
y = 3
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