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Question
Find the value of x, if
\[\begin{vmatrix}2x & 5 \\ 8 & x\end{vmatrix} = \begin{vmatrix}6 & 5 \\ 8 & 3\end{vmatrix}\]
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Solution
\[\text{ Given }: \begin{vmatrix}2x & 5 \\ 8 & x\end{vmatrix} = \begin{vmatrix}6 & 5 \\ 8 & 3\end{vmatrix}\]
\[ \Rightarrow 2 x^2 - 40 = 18 - 40\]
\[ \Rightarrow 2 x^2 = 18\]
\[ \Rightarrow x^2 = 9\]
\[ \Rightarrow x = \pm 3\]
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