3 and 4 .Determinants and Matrices
easy

यदि $A = \left[ {\begin{array}{*{20}{c}}1&2\\{ - 3}&0\end{array}} \right]$ और $B = \left[ {\begin{array}{*{20}{c}}{ - 1}&0\\2&3\end{array}} \right]$, तो  

A

${A^2} = A$

B

${B^2} = B$

C

$AB \ne BA$

D

$AB = BA$

Solution

(c) चुकी  ${A^2} = \left[ {\begin{array}{*{20}{c}}1&2\\{ – 3}&0\end{array}} \right]\,\left[ {\begin{array}{*{20}{c}}1&2\\{ – 3}&0\end{array}} \right] = \left[ {\begin{array}{*{20}{c}}{ – 4}&2\\{ – 3}&{ – 6}\end{array}} \right] \ne A$                    

  ${B^2} = \left[ {\begin{array}{*{20}{c}}{ – 1}&0\\2&3\end{array}} \right]\,\left[ {\begin{array}{*{20}{c}}{ – 1}&0\\2&3\end{array}} \right] = \left[ {\begin{array}{*{20}{c}}1&0\\4&9\end{array}} \right] \ne B$                       

अब, $AB = \left[ {\begin{array}{*{20}{c}}1&2\\{ – 3}&0\end{array}} \right]\,\left[ {\begin{array}{*{20}{c}}{ – 1}&0\\2&3\end{array}} \right] = \left[ {\begin{array}{*{20}{c}}3&6\\3&0\end{array}} \right]$                  

  तथा $BA = \left[ {\begin{array}{*{20}{c}}{ – 1}&0\\2&3\end{array}} \right]\,\left[ {\begin{array}{*{20}{c}}1&2\\{ – 3}&0\end{array}} \right] = \left[ {\begin{array}{*{20}{c}}{ – 1}&{ – 2}\\{ – 7}&4\end{array}} \right]$                     

  स्पष्टत: $AB \ne BA$.

Standard 12
Mathematics

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