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2 problems match “functional inequalities”. Clear

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  1. Possible values of f(2018) ●●●○○ 50 ptsLet f:Z→Zf: \mathbb{Z} \rightarrow \mathbb{Z} be an even function with f(1)=1f(1)=1 and f(2017)≠1f(2017) \neq 1. For all integers x,yx, y, 2f(x+y)−f(x)−f(y)⩽∣f(x)−f(y)∣2f(x+y)-f(x)-f(y) \leqslant |f(x)-f(y)|. Find the value of f(2018)f(2018).
  2. Smallest bound on function differences ●●●○○ 50 ptsThe function f(x)f(x) is defined on [0,1][0,1] and satisfies f(0)=f(1)f(0)=f(1), and for any x,y∈[0,1]x, y \in [0,1] with x≠yx \neq y, we have ∣f(x)−f(y)∣<∣x−y∣|f(x)-f(y)|<|x-y|. Find the smallest real number mm such that for every such function ff and any x,y∈[0,1]x, y \in [0,1], we have ∣f(x)−f(y)∣<m|f(x)-f(y)|<m. Give your answer as a decimal.