MCQ
Given that $\left[\begin{array}{ll}1 & x\end{array}\right]\left[\begin{array}{cc}4 & 0 \\ -2 & 0\end{array}\right]=0$, the value of $x$ is ;
- A$-4$
- B$-2$
- ✓$2$
- D$4$
✓
Answer
Correct option: C.
$2$
We have $,\left[\begin{array}{ll}1 & x\end{array}\right]\left[\begin{array}{cc}4 & 0 \\ -2 & 0\end{array}\right]=0$
$ \Rightarrow [1 \times 4+x \times(-2) 1 \times 0+x \times 0]=\left[0 0\right]$
$\Rightarrow 4-2 x=0 $
$\Rightarrow 4=2 x $
$\Rightarrow x=2$
$ \Rightarrow [1 \times 4+x \times(-2) 1 \times 0+x \times 0]=\left[0 0\right]$
$\Rightarrow 4-2 x=0 $
$\Rightarrow 4=2 x $
$\Rightarrow x=2$
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