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If alpha,beta are the roots of the equat...

If `alpha,beta` are the roots of the equation `x^(2) - 4x + 8 = 0`. Them for any `ninN,alpha^(2n)+beta^(2n)` equals

A

`2^(2n+1)"cos"(n pi)/(2)`

B

`2^(3n)"cos"(n pi)/(2)`

C

`2^(3n+1)"cos"(n pi)/(2)`

D

`2^(3n)"cos"(n pi)/(4)`

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