1.

if 1,ω,ω² are three cube roots of unity, prove that (1+5ω²+ω⁴)(1+5ω+ω²)(5+ω+ω²)=64

Answer»

Formulas to be used:

1) 1+ω+ω2=0

2) ω3k=1,ω3k+1=ω,ω3k+22

So,(1+5ω²+ω⁴)(1+5ω+ω²)(5+ω+ω²)

(1+5ω2+ω)(1+5ω+ω2)(5+ω+ω2)

So, 1+ω=-ω2,1+ω2=-ω, ω+ω2=-1

(5ω22)(5ω-ω)(5-1)

(4ω2)(4ω)(4)

64ω3=64

Hence Proved

(1 + 5ω2 + ω4) (1 + 5ω + ω2) ( 5 + ω + ω2)

= (1 + ω + ω2 + 4ω2) ( 1 + ω + ω2 + 4ω) ( 4 +1 + ω + ω2)    (∵ ω3 = 1 ⇒ ω4 = ω)

= 4ω2.4ω.4      (∵ 1 + ω + ω2 = 0)

= 64ω3 = 64     (∵ ω3 = 1)



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