[ 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.

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

(a) :
$
\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] } & =\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]
\end{aligned}
$

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