[ lll 7 & 1 & 2 9 & 2 & 1 ] [ l 3 4 5 ]+2 [ l 4 2 ] is equal to - Vidyadip

MCQ

$\left[\begin{array}{lll}7 & 1 & 2 \\ 9 & 2 & 1\end{array}\right]\left[\begin{array}{l}3 \\ 4 \\ 5\end{array}\right]+2\left[\begin{array}{l}4 \\ 2\end{array}\right]$ is equal to

✓
$\left[\begin{array}{l}43 \\ 44\end{array}\right]$
B
$\left[\begin{array}{l}43 \\ 45\end{array}\right]$
C
$\left[\begin{array}{l}45 \\ 44\end{array}\right]$
D
$\left[\begin{array}{l}44 \\ 45\end{array}\right]$

✓

Answer

Correct option: A.

$\left[\begin{array}{l}43 \\ 44\end{array}\right]$

$\begin{aligned} {\left[\begin{array}{lll} 7 & 1 & 2 \\ 9 & 2 & 1 \end{array}\right]\left[\begin{array}{l} 3 \\ 4 \\ 5 \end{array}\right]+2\left[\begin{array}{l} 4 \\ 2 \end{array}\right] } \end{aligned} $
$=\left[\begin{array}{c}21+4+10 \\ 27+8+5\end{array}\right]+\left[\begin{array}{l}8 \\ 4\end{array}\right]$
$=\left[\begin{array}{l}35 \\ 40\end{array}\right]+\left[\begin{array}{l}8 \\ 4\end{array}\right]$
$=\left[\begin{array}{l}43 \\ 44\end{array}\right]$

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