数学试题讲解

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设

A = (\begin{array}{cccc} 1 & - 1 & - 1 & - 1 \\ - 1 & 1 & - 1 & - 1 \\ - 1 & - 1 & 1 & - 1 \\ - 1 & - 1 & - 1 & 1 \end{array}), f (x) = 1 + x + x^{2} + \dots + x^{2 n + 1}

, 则

f (A) =