OCR C3 Specimen — Question 3

Exam BoardOCR
ModuleC3 (Core Mathematics 3)
SessionSpecimen
TopicFixed Point Iteration

3 The sequence defined by the iterative formula $$x _ { n + 1 } = \sqrt [ 3 ] { } \left( 17 - 5 x _ { n } \right)$$ with \(x _ { 1 } = 2\), converges to \(\alpha\).
  1. Use the iterative formula to find \(\alpha\) correct to 2 decimal places. You should show the result of each iteration.
  2. Find a cubic equation of the form $$x ^ { 3 } + c x + d = 0$$ which has \(\alpha\) as a root.
  3. Does this cubic equation have any other real roots? Justify your answer.