2018 Putnam B Problems/Problem 2: Difference between revisions
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==Problem== | |||
Let \( n \) be a positive integer, and let \( f_n(z) = n + (n-1)z + (n-2)z^2 + \dots + z^{n-1} \). Prove that \( f_n \) has no roots in the closed unit disk \( \{z \in \mathbb{C}: |z| \leq 1 \} \). | Let \( n \) be a positive integer, and let \( f_n(z) = n + (n-1)z + (n-2)z^2 + \dots + z^{n-1} \). Prove that \( f_n \) has no roots in the closed unit disk \( \{z \in \mathbb{C}: |z| \leq 1 \} \). | ||
==Solution== | |||
{{MAA Notice}} | |||
Revision as of 15:56, 18 August 2025
Problem
Let \( n \) be a positive integer, and let \( f_n(z) = n + (n-1)z + (n-2)z^2 + \dots + z^{n-1} \). Prove that \( f_n \) has no roots in the closed unit disk \( \{z \in \mathbb{C}: |z| \leq 1 \} \).
Solution
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