Question

Find the value of x from the following : \[\begin{vmatrix}x & 4 \\ 2 & 2x\end{vmatrix} = 0\]

Answer 1

\[\begin{vmatrix}x & 4 \\ 2 & 2x\end{vmatrix} = 0\] 
\[ \Rightarrow 2 x^2 - 8 = 0\] 
\[ \Rightarrow 2 x^2 = 8\] 
\[ \Rightarrow x^2 = \frac{8}{2} = 4\] 
\[ \Rightarrow x = \sqrt{4} = \pm 2\]