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Answer the following: If ω is a complex cube root of unity, prove that (1 − ω + ω2)6 +(1 + ω − ω2)6 = 128

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Question

Answer the following:

If ω is a complex cube root of unity, prove that (1 − ω + ω2)6 +(1 + ω − ω2)6 = 128

Sum
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Solution

ω is the complex cube root of unity

∴ ω3 = 1 and 1 + ω + ω2 = 0

Also, 1 + ω2 = – ω, 1 + ω = – ω2

∴ L.H.S. = (1 – ω + ω2)6 + (1 + ω – ω2)6

= [(1 + ω2) – ω]6 + [(1 + ω) – ω2]6

= (–ω – ω)6 + (–ω2 – ω2)6

= (–2ω)6 + (–2ω2)6

= 64ω6 + 64ω12

= 64(ω3)2 + 64(ω3)4

= 64(1)2 + 64(1)4

= 128

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Chapter 1: Complex Numbers - Miscellaneous Exercise 1.2 [Page 22]

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Balbharati Mathematics and Statistics 2 (Arts and Science) [English] Standard 11 Maharashtra State Board
Chapter 1 Complex Numbers
Miscellaneous Exercise 1.2 | Q II.19 | Page 22

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