If $\left|\begin{array}{cc}2 x & 2 \\ 4 & x\end{array}\right|=10$, then $x$ is:

$\pm 2$ $\pm 3$ $\pm 4$ 0

$\pm 3$

$\left|\begin{array}{cc}2 x & 3 \\ 4 & x\end{array}\right|=10$ $\Rightarrow (2 x)(x)-(2)(4)=10$ $\Rightarrow 2 x^2-8=10$ $2 x^2=10-8$ $\Rightarrow  2 x^2=18$ $\Rightarrow x^2=9$ $\Rightarrow x= \pm 3$