Question

$\left[\begin{array}{c}x\\ 3\end{array}\begin{array}{c}6\\ 2x\end{array}\right]$ is a singular matrix, then $x$ is equal to

• A. $\pm 3$
• B. $2$
• C. $3$
• D. $4$

Answer 1

The correct option is A $\pm 3$

Let $A=$$\left[\begin{array}{c}x\\ 3\end{array}\begin{array}{c}6\\ 2x\end{array}\right]$.

Given $A$ to be singular.

Then $|A|=0$

or,$2x^2-18=0$

or, $x^2=9$

or,$x=\pm 3$.