If $\left|\begin{array}{cc}2 x & 2 \\ 4 & x\end{array}\right|=10$, then $x$ is:
Answer & explanation
Correct answer: option 2
$\left|\begin{array}{cc}2 x & 3 \\ 4 & x\end{array}\right|=10$
$\Rightarrow (2 x)(x)-(2)(4)=10$
$\Rightarrow 2 x^2-8=10$
$2 x^2=10-8$
$\Rightarrow 2 x^2=18$
$\Rightarrow x^2=9$
$\Rightarrow x= \pm 3$