A-level · Sequences & series

Sigma notation and recurrence relationsExam-style questions

Reading and evaluating sums written with Σ, and generating sequences from a recurrence relation — including spotting periodic behaviour.

27 questions · A-level level · mark scheme and worked solution on each · no sign-up to try

DifficultyAllLevel 2Level 3Level 4Level 5
  1. 1
    Evaluate ∑r=110(2r+1)\displaystyle\sum_{r=1}^{10} (2r + 1).
    Level 3 · 2 marksTry it
  2. 2
    A sequence is defined by un+1=2un−1u_{n+1} = 2u_n - 1 with u1=3u_1 = 3. Find u2u_2, u3u_3 and u4u_4.
    Level 3 · 2 marksTry it
  3. 3
    Evaluate ∑r=120(3r−2)\displaystyle\sum_{r=1}^{20} (3r - 2).
    Level 3 · 2 marksTry it
  4. 4
    (a) Evaluate ∑r=115(5r−3)\displaystyle\sum_{r=1}^{15} (5r - 3). (3 marks)
    (b) Hence evaluate ∑r=615(5r−3)\displaystyle\sum_{r=6}^{15} (5r - 3). (2 marks)
    Level 3 · 5 marksTry it
  5. 5
    A sequence is defined by u1=2u_{1} = 2 and un+1=1unu_{n+1} = \dfrac{1}{u_{n}}.
    (a) Write down u2u_{2} and u3u_{3}, and describe the behaviour of the sequence. (2 marks)
    (b) Write down u50u_{50}. (1 mark)
    (c) Find ∑n=150un\displaystyle\sum_{n=1}^{50} u_{n}. (2 marks)
    Level 3 · 5 marksTry it

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