MCQ
$\left(\frac{\sqrt{3}+ i }{2}\right)^6+\left(\frac{ i -\sqrt{3}}{2}\right)^6$ is equal to
  • $-2$
  • B
    $0$
  • C
    2
  • D
    1

Answer

Correct option: A.
$-2$
(A)
$\left(\frac{\sqrt{3}+ i }{2}\right)^6+\left(\frac{ i -\sqrt{3}}{2}\right)^6$
$=\left(\frac{-1+\sqrt{3} i }{2 i }\right)^6+\left(\frac{-1-\sqrt{3} i }{2 i }\right)^6$
$=\frac{1}{i^6}\left[(\omega)^6+\left(\omega^2\right)^6\right]$
$\ldots\left[\because \omega=\frac{-1+\sqrt{3} i }{2}, \omega^2=\frac{-1-\sqrt{3} i }{2}\right]$
$=-\left[\left(\omega^3\right)^2+\left(\omega^3\right)^4\right]=-(1+1)=-2$

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