-->

Determinants

Question
CBSEENMA12035772

Using properties of determinants, prove that 

open vertical bar table row cell straight x space end cell cell straight x plus straight y space end cell cell straight x plus 2 straight y space end cell row cell straight x plus 2 straight y space end cell cell straight x space end cell cell straight x plus straight y end cell row cell straight x plus straight y space end cell cell straight x plus 2 straight y space end cell cell straight x space end cell end table close vertical bar space equals space 9 straight y squared left parenthesis straight x plus straight y right parenthesis

Solution
open vertical bar table row cell straight x space end cell cell straight x plus straight y space end cell cell straight x plus 2 straight y space end cell row cell straight x plus 2 straight y space end cell cell straight x space end cell cell straight x plus straight y end cell row cell straight x plus straight y space end cell cell straight x plus 2 straight y space end cell cell straight x space end cell end table close vertical bar
Applying space straight R subscript 1 rightwards arrow straight R subscript 1 space plus straight R subscript 2 space plus space straight R subscript 3 space we space get colon
open vertical bar table row cell 3 left parenthesis straight x plus straight y right parenthesis end cell cell 3 left parenthesis straight x plus straight y right parenthesis end cell cell 3 left parenthesis straight x plus straight y right parenthesis end cell row cell straight x plus 2 straight y end cell straight x cell straight x plus straight y end cell row cell straight x plus straight y end cell cell straight x plus 2 straight y end cell straight x end table close vertical bar
space equals space 3 left parenthesis straight x plus straight y right parenthesis space open vertical bar table row 1 1 1 row cell straight x plus 2 straight y end cell straight x cell straight x plus straight y end cell row cell straight x plus straight y end cell cell straight x plus 2 straight y end cell straight x end table close vertical bar
Applying space straight C subscript 1 rightwards arrow straight C subscript 1 minus straight C subscript 2 space and space straight C subscript 2 space rightwards arrow straight C subscript 2 minus straight C subscript 3 space we space get colon
3 left parenthesis straight x plus straight y right parenthesis space open vertical bar table row 0 0 1 row cell 2 straight y end cell cell negative straight y end cell cell straight x plus straight y end cell row cell negative straight y end cell cell 2 straight y end cell straight x end table close vertical bar
equals space 3 left parenthesis straight x plus straight y right parenthesis open vertical bar table row cell 2 straight y end cell cell negative straight y end cell row cell negative straight y end cell cell 2 straight y end cell end table close vertical bar space equals space 3 left parenthesis straight x plus straight y right parenthesis left parenthesis 4 straight y squared minus straight y squared right parenthesis space equals space 9 straight y squared space left parenthesis straight x plus straight y right parenthesis
space RHS equals space LHS
Hence space Proved

Some More Questions From Determinants Chapter