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

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