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if omega ne 1 is a cube root of unity a...

if` omega ne 1` is a cube root of unity and `x+y +x ne 0,` then prove that `|{:((x )/(1+ omega),,(y)/(omega+omega^(2)),,(z)/(omega^(2)+1)),((y)/(omega+omega^(2)),,(z)/(omega^(2)+1),,(x)/(1+omega)),((z)/(omega^(2)+1),,(x)/(1+omega),,(y)/(omega+omega^(2))):}|`

A

`x^(2)+y^(2)+z^(2)=0`

B

`x+yomega+zomega^(2)=0` or `x=y=z`

C

`x ne y ne z ne 0`

D

x=2y=3z

Text Solution

Verified by Experts

The correct Answer is:
B
`(b)` As `1+omega+omega^(2)=0`
`D=|{:(-(x)/(omega^(2)),-y,-(z)/(omega)),(-y,-(z)/(omega),-(x)/(omega^(2))),(-(z)/(omega),-(x)/(omega^(2)),-y):}|=x^(3_+y^(3)+z^(3)-3xyz`
`=(1)/(2)(x+y+z){(x-y)^(2)+(y-z)^(2)+(z-x)^(2)}`
`=(x+y+z)(x+yomega+zomega^(2))(x+yomega^(2)+zomega)`
The determinant varnishes if `x=y=z` or `x+yomega+zomega^(2)=0`
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