If z^ 2 + z + 1 = 0, z ℂ, then | _ n=1 ^ 15 (z^n + (-1)^n 1 z^n )^2 | is equal to _____.

JEE Main 2022 Mathematics question

If , z ℂ, then is equal to .

Answer: 2

z is a primitive cube root of unity or . Expanding, . Over n = 1 to 15, $Σ

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Question ID VK-025276