Question on: JAMB Mathematics - 2014
Find y, if (\begin{pmatrix}
5 & -6 \
2 & -7
\end{pmatrix}\begin{pmatrix}
5 \
2
\end{pmatrix} = \begin{pmatrix}
7 \
-11
\end{pmatrix})
A
8
B
5
C
3
D
2
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Correct Option: C
(\begin{pmatrix}
5 & -6 \
2 & -7
\end{pmatrix}\begin{pmatrix}
5 \
2
\end{pmatrix} = \begin{pmatrix}
7 \
-11
\end{pmatrix})
By matrices multiplication;
5x - 6y = 7 ........(1)
2x - 7y = -11 ......(2)
2 x (1): 10x - 12y = 14 .......(3)
5 x (2): 10x - 35y = -55 ......(4)
(3) - (4): 23y = 69
y = 69/23 = 3
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