+91-8076753736[email protected]
logo
logo
-->

Determinants

Question
CBSEENMA12034784
Wired Faculty App

Solve the following system of equations by matrix method:
3x – 2y + 3z = 8
2x + y – z = 1
4x – 3y + 2z = 4

Solution
The given equations are
3x – 2y + 3z = 8
2x + y – z = 1
4x – 3y + 2z = 4
These equations can be written as
                open square brackets table row 3 cell space space minus 2 end cell cell space space space space space space 3 end cell row 2 cell space space space space space 1 end cell cell space minus 1 end cell row 4 cell space space minus 3 end cell cell space space space 2 end cell end table close square brackets space open square brackets table row straight x row straight y row straight z end table close square brackets space equals space open square brackets table row 8 row 1 row 4 end table close square brackets
or     AX space equals space straight B space where space straight A space equals space open square brackets table row 3 cell space minus 2 end cell cell space space space space space 3 end cell row 2 cell space space space space space 1 end cell cell space space minus 1 end cell row 4 cell space minus 3 end cell cell space space space space space 2 end cell end table close square brackets comma space space space straight X space equals space open square brackets table row straight x row straight y row straight z end table close square brackets comma space space space straight B space equals space open square brackets table row 8 row 1 row 4 end table close square brackets
       open vertical bar straight A close vertical bar space equals space open vertical bar table row 3 cell space space space minus 2 end cell cell space space space space 3 end cell row 2 cell space space space space space 1 end cell cell negative 1 end cell row 4 cell space minus 3 end cell cell space space space 2 end cell end table close vertical bar space equals space 3 space open vertical bar table row cell space space 1 end cell cell space space space minus 1 end cell row cell negative 3 end cell cell space space space space space space 2 end cell end table close vertical bar minus left parenthesis negative 2 right parenthesis space open vertical bar table row 2 cell space space space minus 1 end cell row 4 cell space space space space space space 2 end cell end table close vertical bar plus 3 space open vertical bar table row 2 cell space space space space space space 1 end cell row 4 cell space space minus 3 end cell end table close vertical bar space space space space equals 3 left parenthesis 2 minus 3 right parenthesis plus 2 left parenthesis 4 plus 4 right parenthesis plus 3 left parenthesis negative 6 minus 4 right parenthesis space equals negative 3 plus 16 minus 30 space equals 17 space not equal to 0 therefore space space space space space straight A to the power of negative 1 end exponent space exists. space space space space space space straight A subscript 11 space equals space open vertical bar table row 1 cell space space space minus 1 end cell row cell negative 3 end cell cell space space space space space space 2 end cell end table close vertical bar space equals space 2 minus 3 space equals space minus 1 space space space space space space straight A subscript 12 space equals space minus open vertical bar table row 2 cell space space space minus 1 end cell row 4 cell space space space space space space 2 end cell end table close vertical bar space equals space minus left parenthesis 4 plus 4 right parenthesis space equals space minus 8 space space space space space straight A subscript 13 space equals space open vertical bar table row 2 cell space space space space space space space 1 end cell row 4 cell space space space minus 3 end cell end table close vertical bar space equals space minus 6 minus 4 space equals negative 10 space space space space space space straight A subscript 21 space equals space minus open vertical bar table row cell negative 2 end cell cell space space space space 3 end cell row cell negative 3 end cell cell space space space 2 end cell end table close vertical bar space equals space minus left parenthesis negative 4 plus 9 right parenthesis space equals space minus 5 space space space space space straight A subscript 22 space equals space open vertical bar table row 3 cell space space space 3 end cell row 4 cell space space space 2 end cell end table close vertical bar space equals space 6 minus 12 space equals space minus 6 space space space space space straight A subscript 23 space equals space minus open vertical bar table row 3 cell space space space minus 2 end cell row 4 cell space space space minus 3 end cell end table close vertical bar space equals space minus left parenthesis negative 9 plus 8 right parenthesis space equals space 1 space space space space straight A subscript 31 space equals space open vertical bar table row cell negative 2 end cell cell space space space space space space space 3 end cell row cell space 1 end cell cell space space minus 1 end cell end table close vertical bar space equals 2 minus 3 space equals space minus 1 space space space straight A subscript 32 space equals space minus open vertical bar table row 3 cell space space space space space space space space 3 end cell row 2 cell space space space minus 1 end cell end table close vertical bar space equals space minus left parenthesis negative 3 minus 6 right parenthesis space equals space 9 space space space straight A subscript 33 space equals space open vertical bar table row 3 cell space space space minus 2 end cell row 2 cell space space space space space 1 end cell end table close vertical bar space equals space 3 plus 4 space equals space 7 space space space space space
therefore space space space space adj. space straight A space equals space open square brackets table row cell negative 1 end cell cell space space minus 8 end cell cell space space space minus 10 end cell row cell negative 5 end cell cell space space space minus 6 end cell cell space space space space space space 1 end cell row cell negative 1 end cell cell space space space space 9 end cell cell space space space space space space 7 end cell end table close square brackets space equals space open square brackets table row cell negative 1 end cell cell space space minus 5 end cell cell space space space minus 1 end cell row cell negative 8 end cell cell space space minus 6 end cell cell space space space space space 9 end cell row cell negative 10 end cell cell space space space 1 end cell cell space space space space 7 end cell end table close square brackets space space therefore space space space straight A to the power of negative 1 end exponent space equals space fraction numerator adj. space straight A over denominator open vertical bar straight A close vertical bar end fraction equals negative 1 over 17 open square brackets table row cell negative 1 end cell cell space space space minus 5 end cell cell space space space minus 1 end cell row cell negative 8 end cell cell space space space minus 6 end cell cell space space space space space 9 end cell row cell negative 10 end cell cell space space space space 1 end cell cell space space space space 7 end cell end table close square brackets Now comma space space space AB space equals space straight B space space space space space rightwards double arrow space space space straight X space space equals space straight A to the power of negative 1 end exponent straight B therefore space space space space space space open square brackets table row straight x row straight y row straight z end table close square brackets space equals space minus 1 over 17 open square brackets table row cell negative 1 end cell cell space minus 5 end cell cell space space minus 1 end cell row cell negative 8 end cell cell space space minus 6 end cell cell space space space space 9 end cell row cell negative 10 end cell cell space space space space 1 end cell cell space space space 7 end cell end table close square brackets space space open square brackets table row 8 row 1 row 4 end table close square brackets space space space rightwards double arrow space space space open square brackets table row straight x row straight y row straight z end table close square brackets space equals space minus 1 over 17 open square brackets table row cell negative 8 minus 5 minus 4 end cell row cell negative 64 minus 6 plus 36 end cell row cell negative 80 plus 1 plus 28 end cell end table close square brackets space space rightwards double arrow space space space space space open square brackets table row straight x row straight y row straight z end table close square brackets space equals space minus 1 over 17 open square brackets table row cell negative 17 end cell row cell negative 34 end cell row cell negative 51 end cell end table close square brackets space space space space space rightwards double arrow space space space space space open square brackets table row straight x row straight y row straight z end table close square brackets space equals space open square brackets table row 1 row 2 row 3 end table close square brackets therefore space space space space space straight x space equals space 1 comma space space space space straight y space equals space 2 comma space space space straight z space equals space 3.

Some More Questions From Determinants Chapter

Mock Test Series

Mock Test Series

NCERT Sample Papers

Entrance Exams Preparation