MCQ
If $\left[\begin{array}{ll}1 & 2 \\ 0 & 0\end{array}\right]\left[\begin{array}{c}3 \\ -p\end{array}\right]=\left[\begin{array}{l}5 \\ 0\end{array}\right]$, then value of $p$ is:
- ✓-1
- B1
- C-2
- D2
✓
Answer
Correct option: A.
-1
(a) -1
Explanation:
$\begin{array}{l}{\left[\begin{array}{cc}1 & 2 \\ 0 & 0\end{array}\right]\left[\begin{array}{c}3 \\ -p\end{array}\right]=\left[\begin{array}{l}5 \\ 0\end{array}\right]} \\ {\left[\begin{array}{c}3-2 p \\ 0-0\end{array}\right]=\left[\begin{array}{l}5 \\ 0\end{array}\right]} \\ \Rightarrow 3-2 p=5 \\ \Rightarrow-2 p=5-3 \\ \Rightarrow-2 p=2\end{array}$
$\Rightarrow p=-1$
Explanation:
$\begin{array}{l}{\left[\begin{array}{cc}1 & 2 \\ 0 & 0\end{array}\right]\left[\begin{array}{c}3 \\ -p\end{array}\right]=\left[\begin{array}{l}5 \\ 0\end{array}\right]} \\ {\left[\begin{array}{c}3-2 p \\ 0-0\end{array}\right]=\left[\begin{array}{l}5 \\ 0\end{array}\right]} \\ \Rightarrow 3-2 p=5 \\ \Rightarrow-2 p=5-3 \\ \Rightarrow-2 p=2\end{array}$
$\Rightarrow p=-1$
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