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
- C2
- D4
✓
Answer
$\begin{array}{l}\text {We have, }\left[\begin{array}{ll}1 & x\end{array}\right]\left[\begin{array}{cc}4 & 0 \\ -2 & 0\end{array}\right]=0 \\ \Rightarrow \quad[1 \times 4+x \times(-2) \quad 1 \times 0+x \times 0]=\left[\begin{array}{ll}0 & 0\end{array}\right] \\ \Rightarrow \quad 4-2 x=0 \Rightarrow 4=2 x \Rightarrow x=2\end{array}$
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