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3 and 4 .Determinants and Matrices
easy
यदि $A = \left[ {\begin{array}{*{20}{c}}1&3\\2&1\end{array}} \right]$, तो ${A^2} - 2A$ के सारणिक का मान होगा
A
$5$
B
$25$
C
$-5$
D
$-25$
Solution
(b) $A = \left| {\,\begin{array}{*{20}{c}} 1&3\\ 2&1 \end{array}\,} \right| $
${A^2} = \left[ {\begin{array}{*{20}{c}}1&3\\2&1\end{array}} \right]\,\left[ {\begin{array}{*{20}{c}}1&3\\2&1\end{array}} \right]\, = \,\left[ {\begin{array}{*{20}{c}}7&6\\4&7\end{array}} \right]$
${A^2} – 2A = \left[ {\begin{array}{*{20}{c}}5&0\\0&5\end{array}} \right]\,,{\rm{det }}({A^2} – 2A) = \left| {\,\begin{array}{*{20}{c}}5&0\\0&5\end{array}\,} \right| = 25$.
Standard 12
Mathematics