olymmath

CMO 1985

Canadian Mathematical Olympiad 1985.

Paper

Problem 5

  • Paper

Let 1<x1<21 < x_1 < 2 and, for n=1n = 1 , 2, …\dots , define xn+1=1+xn−12xn2x_{n + 1} = 1 + x_n - \frac{1}{2} x_n^2 . Prove that, for n≥3n \ge 3 , ∣xn−2∣<2−n|x_n - \sqrt{2}| < 2^{-n} .

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