Edexcel Paper 1 2018 June — Question 4

Exam BoardEdexcel
ModulePaper 1 (Paper 1)
Year2018
SessionJune
TopicFixed Point Iteration

  1. The curve with equation \(y = 2 \ln ( 8 - x )\) meets the line \(y = x\) at a single point, \(x = \alpha\).
    1. Show that \(3 < \alpha < 4\)
    \begin{figure}[h]
    \includegraphics[alt={},max width=\textwidth]{b5f50f17-9f1b-4b4c-baf3-e50de5f2ea9c-08_666_1061_445_502} \captionsetup{labelformat=empty} \caption{Figure 2}
    \end{figure} Figure 2 shows the graph of \(y = 2 \ln ( 8 - x )\) and the graph of \(y = x\).
    A student uses the iteration formula $$x _ { n + 1 } = 2 \ln \left( 8 - x _ { n } \right) , \quad n \in \mathbb { N }$$ in an attempt to find an approximation for \(\alpha\).
    Using the graph and starting with \(x _ { 1 } = 4\)
  2. determine whether or not this iteration formula can be used to find an approximation for \(\alpha\), justifying your answer.