A Zero Through a Substitution

Problem

Let f(u)=u2+au+b2f(u) = u^2 + au + b - 2, where u=x+1xu = x + \dfrac{1}{x} for real x0x \neq 0. If the composite function of xx has a zero, find the minimum value of a2+b2a^2 + b^2.

Answer

Solution

Difficulty7/10
Topicsfunctions, Substitution, Cauchy-Schwarz, inequality

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