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If Matrix a = [ a I J ] 2 × 2 Where a I J = { 1 , I F I ≠ J 0 , I F I = J - Mathematics

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Question

If matrix  \[A = \left[ a_{ij} \right]_{2 \times 2}\] where 

\[a_{ij} = \begin{cases}1 & , if i \neq j \\ 0 & , if i = j\end{cases}\] 

 

Options

  • I

  • A

  • O

  • -I

MCQ
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Solution

Given: 

\[a_{ij} = \begin{cases}1 & , if i \neq j \\ 0 & , if i = j\end{cases}\]


\[\therefore a_{11} = 0\] 

\[ a_{12} = 1\] 

\[ a_{21} = 1\] 

\[ a_{22} = 0\] 

\[\text{Therefore}, matrix  A = \begin{bmatrix}0 & 1 \\ 1 & 0\end{bmatrix}\] 

\[ A^2 = \begin{bmatrix}0 & 1 \\ 1 & 0\end{bmatrix}\begin{bmatrix}0 & 1 \\ 1 & 0\end{bmatrix}\] 

\[ = \begin{bmatrix}0 + 1 & 0 + 0 \\ 0 + 0 & 1 + 0\end{bmatrix}\] 

\[ = \begin{bmatrix}1 & 0 \\ 0 & 1\end{bmatrix}\] 

 = I 

 Hence, the correct option is (a).

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Chapter 5: Algebra of Matrices - Exercise 5.7 [Page 69]

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RD Sharma Mathematics [English] Class 12
Chapter 5 Algebra of Matrices
Exercise 5.7 | Q 40 | Page 69

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