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CAPE Pure Mathematics Unit 2 · May/June 2012 · Paper 2 · Question 3(a)(ii)

For a geometric progression, u_6 = 486 and u_{11} = 118\,098, where u_n is the n^{\text{th}} term.

Hence, calculate n if S_n = 177\,146.

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Other parts of this question

  1. 3(a)(i)Calculate the first term, a, and the common ratio, r.[5 marks]
  2. 3(b)(i)Express, in terms of r, the r^{\text{th}} term, u_r, of the sequence.[2 marks]
  3. 3(b)(ii)Prove, by mathematical induction, that \sum_{r=1}^n u_r = \frac{1}{6}n(n + 1)(2n + 7), \forall n \in \mathbb{N}.[7 marks]
  4. 3(c)(i)Use Maclaurin's Theorem to find the first three non-zero terms in the power series expansion of \cos 2x.[5 marks]
  5. 3(c)(ii)Hence, or otherwise, obtain the first two non-zero terms in the power series expansion of \sin^2 x.[2 marks]

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