Question

Find the value of x from the following : $\left|\begin{array}{cc}x& 4\\ 2& 2x\end{array}\right|=0$

Answer 1

$$\begin{gathered} \left|\begin{array}{cc}x& 4\\ 2& 2x\end{array}\right|=0 \\ \Rightarrow 2x^2-8=0 \\ \Rightarrow 2x^2=8 \\ \Rightarrow x^2=\frac{8}{2}=4 \\ \Rightarrow x=\sqrt{4}=\pm 2 \end{gathered}$$