Complex number ω satisfies ω5=2. Find the sum of all possible values of ω4+ω3+ω2+ω+1
Solution
Solution:
The value of ω4+ω3+ω2+ω+1=ω−1ω5−1=ω−11. The sum of these values is therefore the sum of ω−11 over the five roots ω. Substituting z=ω−1, we have that (z+1)5=2, so z5+5z4+10z3+10z2+5z−1=0. The sum of the reciprocals of the roots of this equation is −−15=5 by Vieta's.
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Source: MathNet,
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