MathDB
f(x+1) = f(x) + 1, f(f(f(O))) = p

Source: Polish MO Second Round 1973 p3

September 8, 2024
algebralimitcalculus

Problem Statement

Let f:RR f:\mathbb{R} \to \mathbb{R} be an increasing function satisfying the following conditions: 1. f(x+1)=f(x)+1 f(x+1) = f(x) + 1 for each xR x \in \mathbb{R} , 2. there exists an integer p such that f(f(f(O)))=p f(f(f(O))) = p . Prove that for every real number x x limnxnn=p3. \lim_{n\to \infty} \frac{x_n}{n} = \frac{p}{3}. where x1=x x_1 = x and xn=f(xn1) x_n =f(x_{n-1}) for n=2,3, n = 2, 3, \ldots .