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
(a) ${\left( {\frac{{\sqrt 3 + i}}{2}} \right)^6} + {\left( {\frac{{i - \sqrt 3 }}{2}} \right)^6} = {\left( {\frac{{ - 1 + \sqrt 3 i}}{{2i}}} \right)^6} + {\left( {\frac{{ - 1 - \sqrt 3 i}}{{2i}}} \right)^6}$
$ = \frac{1}{{{i^6}}}[{(\omega )^6} + {({\omega ^2})^6}] = - [{({\omega ^3})^2} + {({\omega ^3})^4}]$

$\left( {\because \,\,\,\omega  = \frac{{ - 1 + \sqrt 3 i}}{2},{\omega ^2} = \frac{{ - 1 - \sqrt 3 i}}{2}} \right)$

$ = - (1 + 1) = - 2$.

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