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Sequences and Series

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Question 99

An arithmetic sequence has first term a a\,a and common difference ddd. The sum of the first 8 terms of the sequence is 330.

a.

Show that 4a+14d=1654a + 14d = 1654a+14d=165.

[2]
b.

Given that the sum of the first 25 terms is 500, find, giving your answer in exact form, the sum of the first 21 terms.

[3]
c.

Sn S_n\,Sn​ is the sum of the first n n\,n terms of the sequence. Explain why the value you found in part (b) is the maximum value of SnS_nSn​.

[2]
Markscheme

Sequences and Series Questions

  1. A Level
  2. /Maths
  3. /Sequences and Series

326 exam-style questions on Edexcel A Level Maths Sequences and Series, covering 3.1 Arithmetic Sequences, 3.2 Arithmetic Series, 3.3 Geometric Sequences, 3.4 Geometric Series, 3.5 Sum to Infinity, 3.6 Sigma Notation, 3.7 Recurrence Relations, and 3.8 Modelling with Series. Each one has a worked solution and a mark scheme showing where the marks go.

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