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Determinants

Question
CBSEENMA12034508

Find the minors and co-factors of the elements a11, a21 in the determinant.

Solution
increment space equals space open vertical bar table row cell straight a subscript 11 end cell cell space straight a subscript 12 end cell cell space straight a subscript 13 end cell row cell straight a subscript 21 end cell cell space straight a subscript 22 end cell cell straight a subscript 23 end cell row cell straight a subscript 31 end cell cell space straight a subscript 32 end cell cell straight a subscript 33 end cell end table close vertical bar
increment space equals space open vertical bar table row cell straight a subscript 11 end cell cell space straight a subscript 12 end cell cell space straight a subscript 13 end cell row cell straight a subscript 21 end cell cell space straight a subscript 22 end cell cell space straight a subscript 23 end cell row cell straight a subscript 31 end cell cell space straight a subscript 32 end cell cell space straight a subscript 33 end cell end table close vertical bar
Minor of straight a subscript 11 space equals space straight M subscript 11 space equals space open vertical bar table row cell straight a subscript 22 end cell cell space space space space straight a subscript 23 end cell row cell straight a subscript 32 end cell cell space space space straight a subscript 33 end cell end table close vertical bar space equals space straight a subscript 22 straight a subscript 33 minus straight a subscript 23 straight a subscript 32

Co-factor of straight a subscript 11 space equals space straight A subscript 11 space equals space left parenthesis negative 1 right parenthesis to the power of 1 plus 1 end exponent straight M subscript 11 space equals space straight M subscript 11 space equals space straight a subscript 22 straight a subscript 33 minus straight a subscript 23 straight a subscript 32
Minor of straight a subscript 21 equals straight M subscript 21 space equals space open vertical bar table row cell straight a subscript 12 end cell cell space space straight a subscript 13 end cell row cell straight a subscript 13 end cell cell space space straight a subscript 33 end cell end table close vertical bar space equals space straight a subscript 12 straight a subscript 33 space minus space straight a subscript 13 straight a subscript 32
Co-factor of straight a subscript 21 space equals space straight A subscript 21 space equals space left parenthesis negative 1 right parenthesis to the power of 2 plus 1 end exponent space space straight M subscript 21 space equals space minus straight M subscript 21 space equals space minus straight a subscript 12 straight a subscript 33 plus straight a subscript 13 straight a subscript 32

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