Question

If \(x_0\) is any positive rational number and \[\begin{equation*} x_1 = \frac{x_0 + 2}{x_0 + 1}, \quad x_2 = \frac{x_1 + 2}{x_1 + 1}, \quad x_3 = \frac{x_2 + 2}{x_2 + 1}, \end{equation*}\]

prove that

  1. \(\sqrt{2}\) lies between \(x_0\) and \(x_1\), and between \(x_2\) and \(x_3\),
  2. \(|x_1^2 - 2| < |x_0^2 - 2|\),
  3. \(|x_2^2 - 2| < \frac{1}{9} |x_0^2 - 2|\).
By taking \(x_0 = \frac{7}{5}\), or otherwise, show that \[\begin{equation*} \frac{41}{29} < \sqrt{2} < \frac{99}{70}, \end{equation*}\]

and, without using tables, show that each of \(\dfrac{41}{29}\) and \(\dfrac{99}{70}\) differ from \(\sqrt{2}\) by less than \(5 \times 10^{-4}\).