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MathNet 2015-part-04 — 191 problems (EN–VI) Question 85

Math Olympiad Vault · MathNet 2015-part-04 — 191 problems (EN–VI)

Question 85

a) Show that, if $I \subset \mathbb{R}$ is a closed bounded interval, and $f: I \to \mathbb{R}$ is a non-constant monic polynomial function such that $\max_{x \in I} |f(x)| \lt 2$, then there exists a non-constant monic polynomial function $g: I \to \mathbb{R}$ such that $\max_{x \in I} |g(x)| \lt 1$.

b) Show that there exists a closed bounded interval $I \subset \mathbb{R}$ such that $\max_{x \in I} |f(x)| \ge 2$ for every non-constant monic polynomial function $f: I \to \mathbb{R}$.