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Question

If A = open square brackets table row 0 1 row cell negative 1 end cell 0 end table close square brackets and (aI2 + bA)2 = A, then -

  1. a = b =square root of 2    
  2. a = b = 1/square root of 2    
  3. a = b =square root of 3    
  4. a = b = 1/square root of 3    

The correct answer is: a = b = 1/square root of 2


    we are given that  A = open square brackets table row 0 1 row cell negative 1 end cell 0 end table close square brackets and (aI2 + bA)2 = A, then we need to find the correct option
    left parenthesis a I plus b A right parenthesis squared space space equals left parenthesis a I plus b A right parenthesis left parenthesis a I plus b A right parenthesis space
equals a squared I squared space plus a b I A plus b a A I plus b squared A squared space space space
equals a squared I plus 2 a b A plus b squared space A squared space space left parenthesis because I space squared equals I comma I A equals A I right parenthesis space
equals a squared I plus 2 a b A minus b squared space I left parenthesis because A space space 2 space space equals negative I right parenthesis
space equals left parenthesis a squared minus b squared space right parenthesis I plus 2 a b A space
E q u a t i n g space c o r r e s p o n d i n g space e l e m e n t s space i n space left parenthesis a I plus b A right parenthesis squared space space a n d space A squared space comma
space w e space g e t space a squared minus b squared space space equals 0 space a n d space 2 a b equals 1
space s o l v i n g space t h i s space w e space g e t space a equals b equals plus-or-minus space fraction numerator 1 over denominator root index blank of 2 end fraction

    Therefore the correct  option is choice 2

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