Edexcel Paper 2 2018 June — Question 5

Exam BoardEdexcel
ModulePaper 2 (Paper 2)
Year2018
SessionJune
TopicNewton-Raphson method
TypeDerive Newton-Raphson formula

  1. The equation \(2 x ^ { 3 } + x ^ { 2 } - 1 = 0\) has exactly one real root.
    1. Show that, for this equation, the Newton-Raphson formula can be written
    $$x _ { n + 1 } = \frac { 4 x _ { n } ^ { 3 } + x _ { n } ^ { 2 } + 1 } { 6 x _ { n } ^ { 2 } + 2 x _ { n } }$$ Using the formula given in part (a) with \(x _ { 1 } = 1\)
  2. find the values of \(x _ { 2 }\) and \(x _ { 3 }\)
  3. Explain why, for this question, the Newton-Raphson method cannot be used with \(x _ { 1 } = 0\)