If a,b,c are roots of y3−3y2+3y+26=0 and ω is cube roots of unity, then the value of a−1b−1+b−1c−1+c−1a−1 equals
A
−3ω2
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B
3ω2
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C
ω2
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D
2ω2
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Solution
The correct option is B3ω2 From given equation (y−1)3=−27 (y−1−3)3=1 ∴y−1−3=(1)1/3 ∴y−1−3=1,ω,ω2 as a,b,c are roots ∴a−1=−3,b−1=−3ω,c−1=−3ω2 ∴a−1b−1+b−1c−1+c−1a−1=1ω+1ωω2ω3=ω2+ω2+ω2=3ω2