If n is a multiple of 3 then the coefficient of x^n in the expansion of _e(1 + x + x^2), |x| < 1, is

JEE Advanced Mathematics question

If is a multiple of 3 then the coefficient of in the expansion of , , is

Answer: (C)

, so

(1 + x + = (1 - - (1 - x) = - + .

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Question ID VK-109985