IMC 1998 · Problem 4

Day 120 points5th IMC · Blagoevgrad, Bulgaria

Statement

The function f:R→Rf : \mathbb{R} \to \mathbb{R} is twice differentiable and satisfies f(0)=2f(0) = 2, f′(0)=−2f'(0) = -2 and f(1)=1f(1) = 1. Prove that there exists a real number ξ∈(0,1)\xi \in (0,1) for which

f(ξ)⋅f′(ξ)+f′′(ξ)=0.f(\xi) \cdot f'(\xi) + f''(\xi) = 0.

Official solution

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