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3 and 4 .Determinants and Matrices
easy
सारणिकों का मान ज्ञात कीजिए:
$\left|\begin{array}{ccc}
3 & -4 & 5 \\
1 & 1 & -2 \\
2 & 3 & 1
\end{array}\right|$
A
$43$
B
$44$
C
$45$
D
$46$
Solution
Let $A=\left[\begin{array}{ccc}3 & -4 & 5 \\ 1 & 1 & -2 \\ 2 & 3 & 1\end{array}\right]$
By expanding along the first row, we have:
$|A| = 3\left| {\begin{array}{*{20}{c}}
1&{ – 2} \\
3&1
\end{array}} \right| + 4\left| {\begin{array}{*{20}{c}}
1&{ – 2} \\
2&1
\end{array}} \right| + 5\left| {\begin{array}{*{20}{c}}
1&1 \\
2&3
\end{array}} \right|$
$ = 3(1 + 6) + 4(1 + 4) + 5(3 – 2)$
$ = 3(7) + 4(5) + 5(1)$
$ = 21 + 20 + 5 = 46$
Standard 12
Mathematics