Question

If $\left|\begin{array}{cc}3& x\\ x& 1\end{array}\right|=\left|\begin{array}{cc}3& 2\\ 4& 1\end{array}\right|$ then $x$ is equal to

• A. $2$
• B. $4$
• C. $8$
• D. $\pm 2\sqrt{2}$

Answer 1

The correct option is D $\pm 2\sqrt{2}$

$\left|\begin{array}{cc}3& x\\ x& 1\end{array}\right|=\left|\begin{array}{cc}3& 2\\ 4& 1\end{array}\right|$
$\Rightarrow 3-x^2=3-8$
$\Rightarrow x^2=8$
$\Rightarrow x=\pm 2\sqrt{2}$