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Question: If a is a complex number such that a<sup>2</sup> + a + 1 = 0, then a<sup>31</sup> is equal to...

If a is a complex number such that a2 + a + 1 = 0, then a31 is equal to

A

a

B

a2

C

0

D

1

Answer

a

Explanation

Solution

Sol. a = 1±142=1±3i2\frac{- 1 \pm \sqrt{1 - 4}}{2} = \frac{- 1 \pm \sqrt{3}i}{2}Ž a =1+3i2\frac{- 1 + \sqrt{3}i}{2} = w

a31 = w31 = w = a Q a = 13i2\frac{- 1 - \sqrt{3}i}{2} = w2

a31 = (w2)31 = w62 = w2 = a