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Question
2x − y = 1
7x − 2y = −7
Solution
\[Given: \hspace{0.167em} 2x - y = 1\]
\[ 7x - 2y = - 7\]
Using Crammer's Rule, we get
\[D = \begin{vmatrix} 2 & - 1\\7 & - 2 \end{vmatrix}| = - 4 + 7 = 3\]
\[ D_1 = \begin{vmatrix}1 & - 1\\- 7 & - 2 \end{vmatrix} = - 2 - 7 = - 9\]
\[ D_2 = \begin{vmatrix}2 & 1 \\7 & - 7 \end{vmatrix} = - 14 - 7 = - 21\]
Now,
\[x = \frac{D_1}{D} = \frac{- 9}{3} = - 3\]
\[y = \frac{D_2}{D} = \frac{- 21}{3} = - 7\]
\[ \therefore x = - 3\text{ and }y = - 7\]
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