A Limit to Uniform Approximation

Problem

Let a∈Ra \in \mathbb{R} be such that for every real bb,

max⁡x∈[0,1]∣x2+ax+b∣≥1.\max_{x \in [0,1]} \left|x^2 + ax + b\right| \ge 1.

Find the range of aa.

Answer

Solution

Difficulty8/10
Topicsfunctions, Extrema, Absolute Value, inequality, Casework

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