Edexcel Paper 1 Specimen — Question 8

Exam BoardEdexcel
ModulePaper 1 (Paper 1)
SessionSpecimen
TopicNewton-Raphson method
TypeShow root in interval

8. $$f ( x ) = \ln ( 2 x - 5 ) + 2 x ^ { 2 } - 30 , \quad x > 2.5$$
  1. Show that \(\mathrm { f } ( x ) = 0\) has a root \(\alpha\) in the interval [3.5,4] A student takes 4 as the first approximation to \(\alpha\).
    Given \(\mathrm { f } ( 4 ) = 3.099\) and \(\mathrm { f } ^ { \prime } ( 4 ) = 16.67\) to 4 significant figures,
  2. apply the Newton-Raphson procedure once to obtain a second approximation for \(\alpha\), giving your answer to 3 significant figures.
  3. Show that \(\alpha\) is the only root of \(\mathrm { f } ( x ) = 0\)