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0580/12 Feb/Mar 2021, Question 14: Linear Sequences and Common Difference

Cambridge IGCSE Mathematics 0580 · Paper 12 (Core) · Calculator · 4 marks

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The question, in short

A sequence begins 29, 22, 15, 8. Write the next two terms and find an expression for the nth term.

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Part (a) · 2 marks

Write down the next two terms of the sequence 29, 22, 15, 8.

  1. 1Term-to-term rule: subtract 7
  2. 28 − 7 = 1, 1 − 7 = −6
  3. 3Next two terms: 1, −6

Answer1 −6

Part (b) · 2 marks

Find the nth term of the sequence.

  1. 1Common difference = −7, so nth term = −7n + k
  2. 2First term: −7 × 1 + k = 29 so k = 36
  3. 3nth term = 36 − 7n

Answer36 − 7n

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