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Determinants

Question
CBSEENMA12034578

If straight A space equals open square brackets table row 2 cell space space space minus 3 end cell row 3 cell space space space space space space 4 end cell end table close square brackets comma space show that straight A squared minus 6 straight A plus 17 space straight I space equals space straight O. Hence find straight A to the power of negative 1 end exponent.

Solution
straight A space equals space open square brackets table row 2 cell space space space minus 3 end cell row 3 cell space space space space space 4 end cell end table close square brackets
therefore space space space straight A squared space equals space open square brackets table row 2 cell space space minus 3 end cell row 3 cell space space space space space 4 end cell end table close square brackets space open square brackets table row 2 cell space space minus 3 end cell row 3 cell space space space space space space 4 end cell end table close square brackets space equals space open square brackets table row cell 4 minus 9 end cell cell space space space minus 6 minus 12 end cell row cell 6 plus 12 end cell cell negative 9 plus 16 end cell end table close square brackets space space equals space open square brackets table row cell negative 5 end cell cell space space minus 18 end cell row 18 cell space space space space space space 7 end cell end table close square brackets
therefore space space space straight A squared minus 6 straight A plus 17 space straight I space equals space open square brackets table row cell negative 5 end cell cell space space space minus 18 end cell row 18 cell space space space space space space space 7 end cell end table close square brackets space minus space 6 open square brackets table row 2 cell space space minus 3 end cell row 3 cell space space space space 4 end cell end table close square brackets space plus space 17 open square brackets table row 1 cell space space 0 end cell row 0 cell space space 1 end cell end table close square brackets
space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space
                                  equals space open square brackets table row cell negative 5 end cell cell space space space space minus 18 end cell row 18 cell space space space space space space space 7 end cell end table close square brackets space plus space open square brackets table row cell negative 12 end cell cell space space space space space space 18 end cell row cell negative 18 end cell cell space space space minus 24 end cell end table close square brackets space plus space open square brackets table row 17 cell space space space 0 end cell row 0 cell space space space 17 end cell end table close square brackets
equals space open square brackets table row cell negative 5 minus 12 plus 17 end cell cell space space space space space minus 18 plus 18 plus 0 end cell row cell 18 minus 18 plus 0 end cell cell space space space space space space space space 7 minus 24 plus 17 end cell end table close square brackets space equals space open square brackets table row 0 cell space space space 0 end cell row 0 cell space space space space 0 end cell end table close square brackets

therefore space space space straight A squared minus 6 straight A space plus space 17 space straight I space equals space straight O space space space space space space rightwards double arrow space space space space 17 space straight I space equals space minus straight A squared plus 6 straight A
rightwards double arrow space space space space space 17 space straight I thin space straight A to the power of negative 1 end exponent space equals space minus straight A squared straight A to the power of negative 1 end exponent space plus space 6 straight A thin space straight A to the power of negative 1 end exponent space space space space space space rightwards double arrow space space space space space 17 space straight A to the power of negative 1 end exponent space equals space minus straight A space plus space 6 straight I
rightwards double arrow space space space space space 17 space straight A to the power of negative 1 end exponent space equals space minus open square brackets table row 2 cell space space space minus 3 end cell row 3 cell space space space space space 4 end cell end table close square brackets space plus space open square brackets table row 1 cell space space space 0 end cell row 0 cell space space space 1 end cell end table close square brackets space space space rightwards double arrow space space space 17 space straight A to the power of negative 1 end exponent space equals space open square brackets table row cell negative 2 end cell cell space space space space space space space space 3 end cell row cell negative 3 end cell cell space space space minus 4 end cell end table close square brackets space plus space open square brackets table row 6 cell space space space 0 end cell row 0 cell space space space 6 end cell end table close square brackets
rightwards double arrow space space space space space space 17 space straight A to the power of negative 1 end exponent space equals space open square brackets table row cell negative 2 plus 6 end cell cell space space space space space space 3 plus 0 end cell row cell negative 3 plus 0 end cell cell space space space minus 4 plus 6 end cell end table close square brackets space space space space space space rightwards double arrow space space space 17 space straight A to the power of negative 1 end exponent space equals space open square brackets table row 4 cell space space space space 3 end cell row cell negative 3 end cell cell space space space space 2 end cell end table close square brackets
rightwards double arrow space space space space space space space space straight A to the power of negative 1 end exponent space equals space 1 over 17 open square brackets table row 4 cell space space space space 3 end cell row cell negative 3 end cell cell space space space space 2 end cell end table close square brackets

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