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If ω is a complex cube root of unity, show that (1 + ω)3 − (1 + ω2)3 = 0 - Mathematics and Statistics

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Question

If ω is a complex cube root of unity, show that (1 + ω)3 − (1 + ω2)3 = 0

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Solution

ω is a complex cube root of unity.

∴ ω3 = 1 and 1 + ω + ω2 = 0

∴ ω + ω2 = – 1, 1 + ω = – ω2 and 1 + ω2 = – ω.

(1 + ω)3 – (1 + ω2)3

= (– ω2)3 – (– ω)3

= – ω6 – (– ω3)

= – (ω3)2 + ω3

= – (1)2 + 1

= – 1 + 1

= 0

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Cube Root of Unity
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Chapter 1: Complex Numbers - Exercise 1.4 [Page 20]

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